The Blues might have stunned the St Andrews crowd even more had not England striker Emile Heskey missed three first-half opportunities.

As it was Chelsea manager Jose Mourinho could only watch in frustration as the draw offered fresh hope to rivals Manchester United.

Chelsea had goals from Asier Del Horno and Damien Duff disallowed but beleaguered Birmingham boss Steve Bruce will be now even more confident of pulling off the great escape.

Heskey sliced a shot horribly high from a good position before wastefully heading Jermaine Pennant's free-kick wide.

Olivier Tebily, the Ivory Coast international, came even closer after 15 minutes with a fierce drive that forced an excellent save from Czech Republic goalkeeper Peter Cech.

Birmingham needed Northern Ireland international Maik Taylor - much maligned after conceding ten goals in two games - to keep out Arjen Robben's toe poke from close range.

But Heskey's misery in front of goal continued throughout the first-half as he hooked another good opportunity high over the crossbar as Chelsea's defence dithered.

And Mourinho could only sit in stunned silence with the rest of his disgruntled backroom staff as Birmingham forced the visitors into a string of errors.

Mourinho probably tore the paint off the St. Andrews dressing room walls at half-time and Didier Drogba was close to breaking the deadlock at the start of the second-half.

Del Horno's cross found the Ivory Coast international in the box and his flicked volley required Taylor to be alert.

Then came the crucial five-minute spell when Chelsea's frustrations piled up. Del Horno had the ball in the net in the 50th minute when he connected with a Robben free-kick but the goal was disallowed with the linesman flagging against Ricardo Carvalho, retreating from an offside position.

And then Damien Duff guided a shot into the net after Frank Lampard's astute pass but the Republic of Ireland interantional was clearly offside.

Mourinho brought on Joe Cole, Hernan Crespo and Michael Essien as time ticked away but Birmingham's midfield refused to give up.

Argentina striker Hernan Crespo wasted a gilt-edged chance in injury time by shooting straight at Taylor as Chelsea lumbered to a draw that will give Sir Alex Ferguson renewed hope that a shock Premiership title can yet be his.