Manchester City manager Manuel Pellegrini says that the club "need" Frank Lampard for their title push.
Lampard, 36, headed the decisive goal as City went level with Chelsea, beaten 5-3 at Tottenham, at the top of the table after a 3-2 win over Sunderland.
The ex-Chelsea midfielder, signed on a short-term contract from New York City, was due to head to the USA but extended his stay until the end of the season.
"Frank is very happy to stay here and we need him here," said Pellegrini.
BBC pundit Martin Keown praised Lampard's achievements, describing him as "remarkable".
"He is fourth now in the Premier League's all-time goalscoring list with 176," Keown told Match of the Day.
"That moves him ahead of Thierry Henry. He just keeps delivering and I'm sure Chelsea aren't happy seeing him do it."
Lampard's decision to stay at Manchester City has not impressed some supporters of New York City.
Fans group the Third Rail said it "publicly denounced" the decision.
Lampard signed for New York after being released by Chelsea in June but could now miss the first three months of the Major League Soccer season.
"For the fans in New York, to see Frank play is an amazing thing," said Pellegrini.
"I hope that he will be there next year. But I think that in this moment the best decision for him, for the club, for New York is to stay here with us."
Lampard's winner against Sunderland came three minutes after he came on as a substitute.
He has now scored five Premier League goals for City in 15 appearances, 12 of which have been as a sub.
"He is a very important player for us," said Pellegrini. "That's why we brought him here at the beginning of the season."
City trailed Chelsea by nine points on 1 November but have since taken 29 points from a possible 33.