Manchester City's expensively assembled squad failed to score for the first time in the Premier League this season on Monday, as a 0-0 draw at West Bromwich Albion wiped out its 2-point lead.
Only a superior goal difference is now keeping City ahead of neighbor Manchester United, which routed Wigan 5-0 on Boxing Day.
Mario Balotelli hit the crossbar and had a goal disallowed but City lacked its usual bite at The Hawthorns.
It could even have been worse for Roberto Mancini's side, with Jerome Thomas hitting the post and Shane Long heading wide for the mid-table side.
Manchester City manager Roberto Mancini feels his players now face a test of their nerve as they head into the second half of the season.
''We know that it's impossible to stay top for all 38 games,'' Mancini said. ''We will probably have another eight or nine games in the next 20 days like this.
''West Bromwich played with all their players around the ball and you have to find a solution if you don't score quickly in the first half.''
City could now begin 2012 in second place as United is in action against Blackburn on Saturday before City play at Sunderland on New Year's Day.
''I think United will win the next game and it's more difficult for us against Sunderland away and then within 48 hours again,'' Mancini said. ''But I'm confident we can do a good job by the end. It's important to stay in with a chance of the title at the end.
''If you want to win the title, we have to try to play well against United. United have a strong team but we are strong enough to do this.''
The trip to the Stadium of Light comes at the start of a hectic month for City, with the first of three games against Liverpool coming two days later and an FA Cup tie for the holders against United also to follow.
''I'm disappointed only because we play Jan. 1 and Jan. 3, and Liverpool play Dec. 29 and the 3rd against us,'' Mancini said. ''I'm not happy with this situation because two days in this moment is not correct. I don't know why this is - well maybe, it's for TV.
''To play twice in 48 hours will make a difference in this moment but we have good concentration and in January that is important.''
