Keegan takes charge of his first game at home to Bolton Wanderers on Saturday evening but must have been delighted with what he saw as understrength Newcastle cruised to a 4-1 win over Championship promotion contenders Stoke.
After a dozen games without defeat, it was unlucky 13 for Stoke and this after Newcastle were forced to play the final hour with only ten men following the dismissal of Emre.
Newcastle were 1-0 up through Michael Owen before the Turkey international saw red but even so found little threat from Stoke as Claudio Cacapa added a second before James Milner and Damien Duff put the icing on the cake with second-half strikes.
But worryingly for Keegan, as United ended their six-match winless run, he faces a midfield crisis against Bolton. He must reckon without the suspended trio of Emre, Alan Smith and Nicky Butt along with Joey Barton while Geremi is on Africa Cup of Nations duty.
Stoke started the match brightly and Shay Given kept out a low Richard Cresswell drive while at the other end Owen lifted a 20-yarder inches over the bar.
But Owen was not to be denied and pounced for his first goal since scoring against Everton in early October. It was Owen's first FA Cup goal for Newcastle and was a typical poacher's finish as he put away Milner's knock-down.
It was just the start the frustrated home crowd wanted and it got better after 20 minutes when St James' Park erupted as the returning Keegan took his seat in the directors' box, sandwiched between billionaire owner Mike Ashley and chairman Chris Mort.
But within nine minutes of his arrival, Keegan saw Newcastle reduced to ten men when Emre saw red after he had required treatment following a lunging tackle by Stoke skipper John Eustace which went unpunished.
Emre sought out Eustace straight away and his reckless challenge produced a deserved straight red from referee Uriah Rennie.
However the dismissal only succeeded in galvinising Newcastle who took a 2-0 lead just after the half-hour mark when Charles N'Zogbia's right-wing corner was glanced in by Cacapa for his first United goal.
Despite being a player short Newcastle dominated the second half and scored a third after 68 minutes when Given's long clearance was headed on by Mark Viduka and Milner, charging forward, drove across Steve Simonsen.
Stoke were then torn to shreds again after 76 minutes when Milner put N'Zogbia clear on the right. He released Duff who nonchalantly put away his opportunity for his first goal of the season.
The Potters did manage a late consolation goal with a delightful finish from Liam Lawrence but that could not stop Newcastle romping to their biggest win of the season.