Clinton Morrison and Emile Heskey were again both on target as Steve Bruce's side comfortably disposed of below-par Middlesbrough to register their third successive Barclays Premiership win.

But Bruce will be sweating over the extent of what appeared to be another hamstring injury sustained by playmaker David Dunn.

Dunn, who has had a difficult time with injuries in 2004, had been providing the kind of ammunition for Morrison and Heskey that had previously been lacking.

Middlesbrough, severely hampered by injuries, had to play second fiddle for long periods and seldom showed the kind of form which had taken them into the top five.

They missed the physical presence in the centre of the park of George Boateng where Robbie Savage was an influential figure for the home side.

And Boro's defence also struggled to cope with the power and pace of Heskey and Morrison before the former went off with a leg injury, although it did not look as serious as Dunn's problem.

When the visitors did mount any sort of challenge up front they were comfortably dealt with by a defence well marshalled by the ever-reliable Matthew Upson.

Middlesbrough had the ball in the net after only three minutes when Jimmy-Floyd Hasselbaink's low shot was deflected home by Blues defender Stan Lazaridis but it was ruled out for offside.

Blues retaliated and Dunn's trickery took him past two defenders into the Boro penalty area before he cut the ball back into the path of Morrison.

The striker had time to steady himself before unleashing a fierce shot which looked goal-bound but was blocked by Franck Queudrue.

But Morrison was not to be denied and after 10 minutes some razor sharp finishing put the home side ahead with his fourth goal in his last four starts.

A clearance by Maik Taylor was flicked on by Heskey to the Republic of Ireland player on the right side of the Boro area and he unleashed a low drive from a tight angle which flew past Mark Schwarzer into the corner of the net.

Boro were forced into a substitution after 23 minutes when striker Mark Viduka, who had been doubtful before the game because of a back injury, was stretchered off after a collision with Kenny Cunningham.

Dunn won City a free-kick in a dangerous position 25 yards out after he was fouled by Queudrue and Savage's dipping curling free-kick was held onto at the second attempt by Schwarzer.

Middlesbrough's best chance of the half fell to Hasselbaink after 40 minutes when he flashed a first-time drive inches wide from a Ray Parlour cross after the ex-Arsenal player had taken advantage of a slip by Upson.

Dunn became the first player to be booked a minute later after lashing out at the ball when it became trapped underneath the body of Colin Cooper.

Darren Carter had a shot deflected inches wide from a Damien Johnson cross but from the resulting corner Heskey doubled the home side's lead in first-half injury time.

Johnson played a short corner to Savage and his first-time cross found Heskey who headed home from close range.

Blues were forced into a substitution after 51 minutes when Heskey, who looked to pick up a leg injury in an aerial challenge, was replaced by Julian Gray.

Then a minute later Dunn, who has been dogged by hamstring injuries, looked distraught after appearing to suffer a similar setback and he made way for Jamie Clapham.

Middlesbrough sensed the chance to salvage something from a game in which they had played second fiddle and it needed Kenny Cunningham to block Bolo Zenden's powerful drive.

But Birmingham were soon back on the offensive and Schwarzer was forced to turn over a curling Savage free-kick at full stretch.

Boro's hopes of a late rally disappeared when Stewart Downing shot across the face of goal in the final minutes.

Teams

Birmingham: Maik Taylor, Tebily, Cunningham, Upson, Lazaridis, Johnson, Savage, Carter, Dunn (Clapham 54), Heskey (Gray 50), Morrison (Melchiot 80).

Subs Not Used: Vaesen, Anderton.

Booked: Dunn.

Goals: Morrison 10, Heskey 45.

Middlesbrough: Schwarzer, Reiziger, Southgate, Cooper (Morrison 81), Queudrue, Parlour, Doriva (Nemeth 61), Zenden, Downing, Viduka (Job 23), Hasselbaink.

Subs Not Used: Nash, McMahon.

Att: 29,082

Ref: S Bennett (Kent).