Manchester City manager Roberto Mancini said his side have a "10% chance" of retaining the Premier League title and said
their defeat to Southampton was their worst performance in three years.
City remain nine points behind leaders
Manchester United, who can extend their lead against Everton on Sunday.
And Mancini believes a United win will all but end City's title challenge.
Asked if City could still win the title, he said: "We have a 10% chance: 12 points is too much at this moment."
Mancini's side fell behind to Jason Puncheon's early goal before Steven Davis made it 2-0 midway through the half.
Manchester City's day to forget
- This was only the seventh time that Manchester City have conceded three goals (never more) in a Premier League game under Roberto Mancini.
- Man City have suffered just two defeats in the Premier League that were heavier than this under Roberto Mancini - 0-3 at home to Arsenal in October 2010 and 0-3 at Liverpool in April 2011.
Stats courtesy of Opta
And although Edin Dzeko pulled one back against the run of play, Saints restored their two-goal advantage shortly after the break with Gareth Barry turning the ball into his own net.
It was no more than Saints deserved against a desperately disappointing City side who Mancini admitted had performed badly.
"It was worse than poor," said the Italian. "We didn't play, it was 11 against two so it's difficult.
"I think this is the worst game in the last two or three years.
"The players played really bad - without strength, without personality. We conceded a goal that I have never seen in my life.
"I was really disappointed with my players today. When we perform like today I'm very angry. The players were away on international duty - that's not an excuse, but it is a reason.
"Some of our players came back on Friday and we played today. This made it difficult. In the end we played badly."
City were missing Carlos Tevez, who Mancini said was absent because of personal reasons but he expects to have him back for the FA Cup fifth-round tie with Leeds United next weekend.
Mancini was also critical of keeper Joe Hart, whose mistake allowed Steve Davis to put Southampton 2-0 up.
"It was a really bad mistake," admitted Mancini.
"But this is not strange. He has made two or three mistakes this year and this is not good for us."
He added: "We need to work more. Because we won last year, we think we are top players but to be top players you have to work.
"It'll be very difficult to win the league. I used to always be optimistic and want to be in this moment, but it's difficult."