Chelsea boss Mourinho watched his champions extend their 100 percent league home record this season to 11 matches thanks to first-half strikes from Argentina striker Hernan Crespo and Netherlands winger Arjen Robben.

Man-of-the-match Crespo tapped in the 25th minute after Birmingham goalkeeper Maik Taylor parried a Robben cross-shot but he could do nothing about the Dutchman's repeat attempt in the 43rd minute.

Birmingham's fourth defeat in five matches leaves them floundering in the relegation zone.

Mourinho restored Frank Lampard, Crespo, Robben, Ricardo Carvalho and Paulo Ferreira to the starting line-up for the New Year's Eve clash.

The champions served notice on Birmingham in the fifth minute when Michael Essien's 25-yard shot forced Taylor into a low parry.

William Gallas spared Chelsea's blushes in the 18th minute after Jermaine Pennant's free kick found Stephen Clemence at the back post.

The midfielder prodded the ball past goalkeeper Petr Cech but France defender Gallas slid in at full stretch to clear the ball off the line.

Emile Heskey then dropped a header on to the top of the Chelsea net six minutes later.

However the west London side stuck to their task and crafted their opener within a minute.

Robben charged forward, squaring for Crespo who in turn squared it to Joe Cole.

The England midfielder picked out Robben's surge into the box and Taylor could only parry the left winger's shot into Crespo's path for his eighth goal of the season.

Crespo could have scored another three within three minutes but for dogged defending, fine goalkeeping and the crossbar.

First Cole pounced on a defensive mix-up to go one-on-one with Taylor. He unselfishly squared for Crespo, whose split-second of hesitation was punished by a last-ditch Gray tackle.

Then Taylor pulled off an excellent parry to deny a Crespo blast before the Argentine headed a Gallas cross on to the bar. Chelsea's second goal came shortly before half time, laid on by Eidur Gudjohnsen.

The Iceland forward's perfectly measured ball found Robben inexplicably unmarked in the penalty box and the confident winger hit a first-time, left-foot shot across Taylor from a wide left angle.

Both sides had good chances soon after the interval, Crespo placing an offside header on to the bar and Walter Pandiani seeing his header cleared off the line by Gudjohnsen.

Taylor blocked another Crespo shot with his feet from point-blank range as Chelsea turned the screw on Birmingham.

Chelsea captain John Terry, on his 250th club appearance, had a 71st-minute header cleared off the line.

The home side then closed out an entertaining match to end the year with a commanding, double-digit, lead over the chasing pack.

Elsewhere, a spirited Aston Villa held Arsenal to a 0-0 draw at Villa Park on dealing another blow to the visitors' Premier League season.

Arsenal, sixth in the table, had few clearcut chances, with midfielder Freddie Ljungberg hitting the bar and defender Kolo Toure missing from close range in the final minutes.

Villa put Arsene Wenger's men under real pressure for most of the second half, with the home side's best chance being squandered by Czech striker Milan Baros.