The Portuguese gave his team a "minus one out of 10" rating for their first 45 minutes at St James' Park and blamed individual errors for gifting the Magpies 2-0 lead.
Asked if that was as badly as the Blues had played under him, Mourinho said: "Yes, for sure.
"I have played so many matches with Chelsea over seven years and we have had some bad performances. I remember one at Middlesbrough in 2005, 2006, something like that, we were losing at half-time 3-0, so we have had a few.
"But this first half, I can rate as one of those performances, yes. I put it down to awful individual performances. When you have so many bad individual performances, it's impossible for a team to be a team."
Newcastle forced their way ahead - and deservedly so - three minutes before the break when Ayoze Perez took advantage of indecisive defending to volley home from Vurnon Anita's cross, and when Georginio Wijnaldum headed home Perez's 60th-minure corner, a fourth successive home win over the Blues looked to be on the cards.
However, Mourinho quickly shuffled his pack and two of his substitutes did the trick when Ramires reduced the deficit with a 79th-minute piledriver and Willian levelled direct from a free-kick with just four minutes remaining.