Chelsea manager Jose Mourinho admitted Birmingham deserved today's unexpected goalless draw against the Premiership leaders at St Andrews.

But Mourinho was adamant Asier Del Horno's second-half strike should not have been ruled out for offside, claiming that Ricardo Carvalho was not interfering with play.

Relegation candidates Birmingham were humiliated 7-0 in their last home game 11 days ago, against Liverpool in the FA Cup.

With 10 players either injured or ineligible, Birmingham manager Steve Bruce could have been forgiven for expecting to receive another hammering from the champions.

But his patched-up team would have been in front at half-time had Emile Heskey taken any of the three chances which came his way - and then they defended with great resolve during a second 45 minutes dominated by the visitors.

Mourinho said: "The result is a fair one. Birmingham fought for 90 minutes. Every one of their players was very committed - and they deserved a point.

"It would have been very nasty for them to have lost a match into which they put absolutely everything.

"But we scored a clear goal. There is no doubt about that. You can say what you want, and your pundits can discuss it. But Del Horno's goal should have stood.

"We didn't deserve to win, because we have only played for 45 minutes. In the first 45 minutes we gave them an easy job to do.

"In the second half we made it very hard for them and we scored a good goal. Carvalho is not offside; he doesn't interfere with the game; he doesn't try to get the ball and he is not impairing the vision of the goalkeeper. It was a clear goal.

"But the emphasis should be on the result, and Birmingham deserved a point for the way they fought. In the second half they had to play with a lot of defensive intensity, and we had a couple of very good chances but didn't take them."

Mourinho insists he is still confident Chelsea will go on to achieve back-to-back titles despite their latest blip, which follows on from the defeat at Fulham a fortnight ago.

In contrast, City manager Bruce was pleased his side had regained their pride - and they left the field to a standing ovation, a sharp contrast to the boos which rang around the ground after their mauling by Rafael Benitez's side.

Bruce said: "With the problems we have got with so many players missing, we are up against it. But the one thing we were looking for was a response after the Liverpool game and for people to do their jobs.

"We rode our luck a bit the longer it went on - but in the first half I would have hoped for us to have taken the lead with the chances we had.

"At least we have restored a little bit of pride, and it has earned us a point in the mini-league we are now facing to stay up between ourselves, Portsmouth and West Brom.

"Everyone produced the performance we have been wanting and needing, and I hope that will give everyone a lift for what is ahead."

Bruce was adamant referee Dermot Gallagher was correct in ruling out Del Horno's second-half effort.

He said: "It is hard enough for the referee and linesman and this grey area about whether someone is interfering with play when offside makes it more difficult.

"As far as I am concerned, if you are in the six-yard box standing in an offside position then you are offside.

"Of course, you are interfering with play. The goal should not stand, simple as that."

Heskey, who has managed only two Premiership goals since August, had three first-half opportunities - the best of which saw him head wide when unmarked from a Jermaine Pennant free kick.

But in the second half Chelsea's controversial striker Didier Drogba was also guilty of failing to convert a couple of decent opportunities.