The club's all-time record goalscorer told BBC's Football Focus that he was "disappointed" and "surprised" by the move, which followed two days of talks between players, management and ownership.
Newcastle's Premier League future is under threat after a run of eight successive defeats, with fans boycotting matches and both owner Mike Ashley and manager John Carver under severe pressure.
With three games left to preserve their top-flight status, former captain and manager Shearer described relegation as a "dreadful feeling" and warned there was "no guarantee" Newcastle would get back into the Premier League soon.
Newcastle are two points above the relegation zone after a week in which Carver accused defender Mike Williamson of being sent off deliberately, Coloccini and goalkeeper Tim Krul reportedly had a row on the team bus, the club held two days of "frank dialogue", Derby boss Steve McClaren turned down the manager's job at St James' Park and Coloccini then shared his thoughts with fans.
'I was disappointed in Coloccini'
AS: "I was surprised that Coloccini had written a letter to the fans asking them to stick with the team. If there is one thing that is pretty much guaranteed at Newcastle, it's that the fans will turn up and support. Despite there being protests and fans not turning up for specific games, there has always been 46,000-plus there. So for a player to come out and ask the fans to still support them, I was a bit taken aback and disappointed in that.
"First and foremost, the players have got to give the fans something to shout about. That has to come first and for a long time the fans haven't had anything to shout about."
'Poor communication at the club'
AS: "Newcastle fans love their football club through thick and thin. It's their life. It's what they work all week for. It depends on the result on Saturday if they have a good week or a bad week, and too many times this season and last season they have had bad weeks.
"It wouldn't be so bad if they could say they have been in a decent cup run but they have been knocked out in cup competitions in the very early rounds because the manager has played weakened teams. Whether the manager has to play weakened teams or he is asked to play weakened teams, nobody knows because there is no communication from anyone at Newcastle United. It's disappointing."
'Another relegation would be devastating'
Shearer is asked whether they would take relegation and a regime change. The Magpies were relegated in 2009, while Shearer was in temporary charge.
AS: "The fans are desperate to stay in the Premier League. They have had a taste of relegation, I had a taste of relegation. It's not nice. It's a dreadful feeling. We were fortunate to get back in the Premier League at the first attempt. The fans would be absolutely devastated if the club was to be relegated again. There is no guarantee they would come back so soon this time."
'Not surprised by McClaren's decision'
Derby manager Steve McClaren was offered the chance to take charge of team matters for the last three games of the season, but turned it down. Shearer is asked whether the former England boss would have made a difference.
AS: "No, I don't think it would have. It's a very difficult club to manage under the current circumstances. The best players are sold. We know Newcastle are a selling club now. You can't continue to sell your best players and hope to achieve something. We all know the ambition is to finish mid-table, which is hard for fans to take."
'Newcastle is a mess'
AS: "It has been another crazy week at Newcastle. It doesn't surprise me. Nothing surprises me at Newcastle, I am afraid. It's a mess, it's a mess. They need desperately to get a win from somewhere, but where is that going to come from? I don't know, because the form has been pretty dreadful and players' confidence is zero. But they have got to scrape a win in the three remaining games."
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NEWCASTLE UNITED v WEST BROM
May 9th
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Newcastle Utd Fixtures ...
2014/15 SEASON
Sunday August 17
NEWCASTLE 0 MAN CITY 2
Krul, Janmaat, Williamson, Coloccini, Dummett, Colback, Anita (63' Obertan), Cabella, Sissoko, Gouffran (74' Aarons), Riviere (83' Perez).
Subs: Haidara, Elliot, S Taylor, Abeid
Saturday August 23
ASTON VILLA 0 NEWCASTLE 0
Krul, Janmaat, Williamson, Coloccini, Dummett, Anita (70' de Jong), Colback, Cabella, Sissoko, Gouffran, Riviere (77' Perez - 90+2' S Taylor).
Subs: Haidara, Elliot, Obertan, Abeid
Tuesday August 26
LC GILLINGHAM 0 NEWCASTLE 1 (Egan OG)
Krul, Janmaat, Coloccini, S Taylor, Haidara, Sissoko, Abeid, Obertan, de Jong (68' Perez), Aarons (60' Cabella), Riviere (86' Gouffran)
Subs: Anita, Ferreyra, Elliot, Dummett
Saturday August 30
NEWCASTLE 3 CRYSTAL PALACE 3 (Janmaat, Aarons, Williamson)
Krul, Janmaat (79' Perez), Williamson, Coloccini, Haidara, Sissoko, Colback, Cabella, de Jong (79' Anita), Gouffran (67' Aarons), Riviere
Subs: Elliot, Obertan, S Taylor, Dummett
Saturday September 13
SOUTHAMPTON 4 NEWCASTLE 0
Krul, Janmaat, Williamson, Coloccini, Haidara, Anita (45' Tiote), Colback, Cabella (69' Perez), Sissoko (90'Ameobi), Gouffran, Riviere
Subs: Elliot, Obertan, S Taylor, Armstrong
Saturday September 20
NEWCASTLE 2 HULL CITY (Cisse 2)
Krul, Janmaat, Williamson, Coloccini, Dummett, Tiote (85' Ameobi), Colback, Sissoko, Cabella, Gouffran (90+4' Perez), Riviere (69' Cisse)
Subs: Anita, Haidara, Elliot, S Taylor
Wednesday September 24
LC CRYSTAL PALACE 2 NEWCASTLE 3 AET (Riviere 2, Dummett)
Elliot, Janmaat (46 Haidara), Coloccini, S Taylor, Dummett, Colback, Abeid, Obertan, Armstrong, Ameobi (66 Sissoko), Riviere (80 Perez)
Subs: Anita, Ferreyra, Cabella, Alnwick
Monday September 29
STOKE CITY 1 NEWCASTLE 0
Krul, Janmaat, Williamson, Coloccini, Dummett, Tiote, Colback, Sissoko, Cabella (74' Ameobi), Gouffran (68' Obertan), Riviere (45' Cisse)
Subs: Anita, Elliot, S Taylor, Armstrong
Saturday October 4
SWANSEA CITY 2 NEWCASTLE 2 (Cisse 2)
Krul, Janmaat, Williamson, Coloccini, Dummett, Obertan, Tiote, Sissoko, Colback (69' Riviere), Gouffran (58' Ameobi), Cisse (85' Perez).
Subs: Anita, Haidara, Cabella, Elliot
Saturday October 18
NEWCASTLE 1 LEICESTER CITY 0 (Obertan)
Krul, Janmaat, S Taylor, Coloccini, Dummett (72' Haidara), Tiote, Anita (59' Perez), Colback, Obertan, Sissoko, Gouffran (90+2' Cabella), Cisse
Subs: Elliot, Abeid, Armstrong
Saturday October 26
TOTTENHAM 1 NEWCASTLE 2 (Ameobi, Perez)
Krul, Janmaat, S Taylor, Coloccini, Dummett, Anita (45' Cabella), Colback, Obertan (45' Ameobi), Sissoko, Gouffran, Perez (79' Haidara)
Subs: R Taylor, Ferreyra, Elliot, Armstrong
Wednesday October 29
LC MAN CITY 0 NEWCASTLE 2 (Aarons, Sissoko)
Elliot, Janmaat (64' Sissoko), Coloccini, Dummett, Haidara, Colback, R Taylor, Abeid, Obertan, Armstrong (65' Riviere), Aarons (46' Ameobi)
Subs: Krul, Gouffran, Perez, Cabella
Saturday November 1
NEWCASTLE 1 LIVERPOOL 0 (Perez)
Elliot, Krul, Janmaat, S Taylor, Coloccini, Dummett, Abeid, Colback, Obertan (27' Aarons), Sissoko), Ameobi (66' Cabella), Cisse (45' Perez)
Subs: R Taylor, Gouffran, Haidara, Elliot
Sunday November 9
WEST BROM 0 NEWCASTLE 2 (Perez, Coloccini)
Krul, Janmaat, Coloccini (78' Williamson), Dummett, Haidara, Abeid, Colback, Cabella (82' R Taylor), Sissoko, Ameobi (78' Gouffran), Perez
Subs: Anita, Cisse, Elliot, Armstrong
Saturday November 22
NEWCASTLE 1 QPR 0 (sissoko)
Krul, Janmaat, Williamson, Dummett, Haidara, R Taylor (34' Gouffran), Colback, Cabella (68' Cisse), Sissoko, Ameobi, Perez (89' Armstrong)
Subs: Anita, Ferreyra, Elliot, Streete
Saturday November 29
WEST HAM 1 NEWCASTLE 0
Elliot, Janmaat (74' S Taylor), Williamson, Dummett, Haidara, Tiote (63' Cabella), Colback, Gouffran (63' Cisse), Sissoko, Ameobi, Perez
Subs: Anita, Riviere, Alnwick, Armstrong
Tuesday December 2
BURNLEY 1 NEWCASTLE 1 (Cisse)
Elliot, Janmaat, Williamson (45' S Taylor), Dummett, Haidara, Abeid, Tiote, Gouffran, Perez (45' Cabella), Ameobi (75' Riviere), Cisse
Subs: Anita, Alnwick, Armstrong, Streete
Saturday December 6
NEWCASTLE 2 CHELSEA 1 (Cisse 2)
Elliot (45' Alnwick), Janmaat, S Taylor, Coloccini, Dummett, Tiote, Colback, Cabella (53' Cisse), Sissoko, Ameobi (83' Williamson), Perez
Subs: Anita, Gouffran, Haidara, Riviere
Saturday December 13
ARSENAL 4 NEWCASTLE 1 (Perez)
Alnwick, Janmaat, Williamson, Coloccini, Dummett, Tiote, Colback, Perez (82' Armstrong), Ameobi (56' Cabella), Gouffran, Cisse (56' Riviere)
Subs: Anita, Haidara, Vuckic, Woodman
Wednesday December 17
LC TOTTENHAM 4 NEWCASTLE 0
Alnwick, Coloccini, Williamson, Haidara, Dummett, Colback, Cabella (80' Vuckic), Gouffran, Perez, Sissoko (73' Anita), Riviere (60' Armstrong)
Subs: Streete, Satka, Woodman, Roberts
Sunday December 21
NEWCASTLE 0 SUNDERLAND 1
Alnwick, Janmaat, S Taylor, Coloccini, Dummett, Tiote (75' Cisse), Colback, Gouffran (59' Armstrong), Sissoko, Ameobi (89' Cabella), Perez
Subs: Williamson, Haidara, Riviere, Woodman
Friday December 26
MANCHESTER UNITED 3 NEWCASTLE 1 (Cisse pen)
Alnwick, Janmaat, S Taylor, Coloccini, Dummett (63' Cabella), Anita, Colback, Gouffran, Sissoko, Armstrong (63' Cisse), Perez (82' Vuckic)
Subs: Williamson, Riviere, Satka, Woodman
Sunday December 28
NEWCASTLE 3 EVERTON 2 (Cisse, Perez, Colback)
Alnwick, Janmaat, Williamson, Coloccini, Dummett, Tiote, Colback, Sissoko, Perez, Gouffran (90+1' Cabella), Cisse (73' Riviere)
Subs: Santon, Anita, S Taylor, Armstrong, Woodman
Thursday January 1 2015
NEWCASTLE 3 BURNLEY 3 (S Taylor, Sissoko, Colback)
Alnwick, Janmaat, Coloccini, S Taylor (Williamson 61), Dummett, Sissoko, Colback Tiote, Gouffran (Haidara 71), Perez, Riviere (Armstrong 57)
Subs: Santon, Anita, Satka, Woodman
Saturday January 3 2015
FAC LEICESTER CITY 1 NEWCASTLE 0
Alnwick, Santon, Williamson, Dummett, Haidara, Tiote, Anita, Vuckic (79' Roberts), Armstrong, Riviere, Cabella
Subs: Gouffran, Campbell, Satka, Bigirimana, Woodman, Gilliead
Saturday January 10 2015
CHELSEA 2 NEWCASTLE 0
Krul, Janmaat, Williamson, Coloccini, Dummett, Anita, Colback, Cabella, Sissoko (84' Riviere), Gouffran (63' Ameobi), Perez
Subs: Santon, Haidara, Vuckic, Satka, Woodman
Saturday January 17 2015
NEWCASTLE 1 SOUTHAMPTON 2 (Gouffran)
Krul, Janmaat, Coloccini, Dummett (80' Williamson), Haidara, Anita (68' Ameobi), Colback, Cabella, Sissoko, Gouffran (68' Riviere), Perez
Subs: Santon, Abeid, Armstrong, Woodman
Saturday January 31 2015
HULL CITY 0 NEWCASTLE 3 (Cabella, Ameobi, Gouffran)
Krul, Janmaat, Williamson, Coloccini, Haidara, Anita, Colback, Cabella (72' Gouffran), Sissoko, Ameobi (90+2' Abeid), Perez (82' Cisse)
Subs: Santon, Obertan, Riviere, Alnwick
Sunday February 8 2015
NEWCASTLE 1 STOKE CITY 1 (Colback)
Krul, Janmaat, Williamson, Coloccini, Haidara, Anita (65' Cisse), Colback, Cabella (69' Obertan), Sissoko, Ameobi (86' Abeid), Perez
Subs: Gouffran, Riviere, Dummett, Woodman
Wednesday February 11 2015
CRYSTAL PALACE 1 NEWCASTLE 1 (Cisse)
Krul, Janmaat, Williamson, Coloccini, Haidara, Sissoko, Colback, Perez (90+1' Riviere), Cabella (86' Dummett), Gouffran, Cisse (78' Abeid)
Subs: R Taylor, Anita, Obertan, Woodman
Saturday February 21 2015
MANCHESTER CITY 5 NEWCASTLE 0
Krul, Janmaat (R Taylor 71), Williamson, Coloccini, Haidara, Colback, Anita (Abeid 46), Gouffran (Obertan 86), Sissoko, Perez, Cisse.
Subs: Ameobi, Riviere, Armstrong, Woodman
Saturday February 28 2015
NEWCASTLE 1 ASTON VILLA 0 (Cisse)
Krul, Janmaat, Williamson, Coloccini, Haidara (61' R Taylor), Obertan (78' Gouffran), Abeid, Sissoko, Ameobi, Cisse, Riviere (73' Perez)
Subs: Anita, Gutierrez, Armstrong, Woodman
Wednesday March 4 2015
NEWCASTLE 0 MANCHESTER UNITED 1
Krul, Janmaat, Williamson, Coloccini, R Taylor (65' Gutierrez), Obertan, Abeid, Sissoko, Ameobi (81' Gouffran), Riviere (59' Perez), Cisse
Subs: Anita. Armstrong, Satka, Woodman
Sunday March 15 2015
EVERTON 3 NEWCASTLE 0
Krul, Janmaat, Williamson, Coloccini, R Taylor, Sissoko, Colback, Obertan (45' Perez), Gouffran, Ameobi (58' Cabella), Riviere (62' Gutierrez)
Subs: Anita, Elliot, Armstrong, Satka
Saturday March 21 2015
NEWCASTLE 1 ARSENAL 2 (Sissoko)
Krul, R Taylor, Janmaat, Williamson, Colback, Anita (72' Gutierrez), Sissoko, Gouffran, Cabella, Ameobi (89' Armstrong), Perez
Subs: Elliot, Obertan, Riviere, Satka, Kemen
Sunday April 5 2015
SUNDERLAND 1 NEWCASTLE 0
Krul, R Taylor, Janmaat, Williamson, Colback, Gouffran (58' Riviere), Gutierrez, Sissoko, Cabella, Perez, Ameobi (87' Armstrong)
Subs: Anita, Elliot, Obertan, Abeid, Kemen
Monday April 13 2015
LIVERPOOL 2 NEWCASTLE 0
Krul, R Taylor, Colback, Anita, Janmaat, Williamson, Cabella, Abeid (75' Armstrong), Perez (86' Gouffran), Sissoko, Obertan (67' Gutierrez)
Subs: Elliot, Ameobi, Riviere, Sterry
Sunday April 19 2015
NEWCASTLE 1 TOTTENHAM HOTSPUR 3 (Colback)
Krul, Janmaat, Williamson, Coloccini, Anita (75' Armstrong), Abeid (45' Obertan), R Taylor, Colback, Gouffran (45' Ameobi), Perez, Cabella
Subs: Riviere, Kemen, Woodman, Sterry
Saturday April 25 2015
NEWCASTLE 2 SWANSEA CITY 3 (Perez, De Jong)
Krul, Janmaat (61' Abeid), Williamson, Coloccini, Anita, Colback, R Taylor, Gutierrez, Cabella (74' de Jong), Riviere (74' Armstrong), Perez
Subs: Gouffran, Obertan, Ameobi, Woodman
Saturday May 2 2015
LEICESTER CITY 3 NEWCASTLE 0
Krul, Janmaat, Williamson, Coloccini, Dummett, Colback, R Taylor (58' de Jong), Gutierrez, Sissoko, Perez (74' Armstrong), Riviere (64' Anita)
Subs: Cabella, Ameobi, Abeid, Woodman
Saturday May 9 2015
Newcastle United v West Brom
Saturday May 16 2015
QPR v Newcastle United
Sunday May 24 2015
Newcastle United v West Ham United