BLACKBURN Rovers safely booked their place in the fourth round of the Carling Cup after a comfortable 3-0 victory over Birmingham City at Ewood Park.

After a goalless first half of frustration in which Birmingham goalkeeper Richard Kingson had to be stretchered off with concussion after colliding with a post, it was David Bentley who finally broke the deadlock after a fine solo strike on 66 minutes.

That settled any nervousness and the home side were able to see out the remainder of the match with comparative ease. Matt Derbyshire doubled the lead from the penalty spot after his run into the area had been checked, and it was left for Roque Santa Cruz to score his first Ewood Park goal to wrap things up as clock ticked onto ninety minutes.

Mark Hughes made five changes from the side that lost to Portsmouth, out of the sixteen went Savage, Pedersen and McCarthy, whilst Warnock and Santa Cruz dropped down to the bench. In their place came young defender Martin Olsson for his first start in a Rovers shirt, whilst Tugay, Mokoena, Derbyshire and Roberts started.

Birmingham boss Steve Bruce took the opportunity to change his entire squad, and that showed as Rovers started positively from the off. Just two minutes had elapsed when a free-kick from Bentley went close. The fans in the Blackburn End thought it was the back of the net that rippled, but alas it was the side-netting where the ball ended up.

The home side continued their early promise, Derbyshire crossed from the right for Roberts who chested the ball goalwards from inside the six-yard box, but goalkeeper Richard Kingson made a brilliant point-blank save. The just before the quarter-hour, Derbyshire saw an effort cleared off the line by Parnaby, and from the resulting corner kick Derbyshire couldn't find the final touch to Emerton's drilled centre.

The one way traffic towards Kingson's showed no signs of stopping, Derbyshire saw a header bounce off the crossbar, but his effort would have been ruled out by the linesman's flag, whilst Dunn saw an effort from distance turned away by the Birmingham 'keeper.

But just like the game against Portsmouth on Sunday, those missed chances almost came home to roost for Rovers as Birmingham tested Brad Friedel through MIkael Forssell. The former Chelsea striker turned well on the edge of the area before shooting goalwards only to see the Rovers' number one, making his 150th consecutive start, turn the ball around the post.

Operating a 4-2-3-1 formation, Rovers saw plenty of the ball, but despite that possession, they rarely got the better of a rigid Birmingham defence. The best chance of the first half came after fine work from Roberts, the striker doing well to find Bentley who immediately released Derbyshire through on goal, but once again Kingson made a vital save.

But just before the break Birmingham were dealt a blow when Kingson had to be stretchered from the field. A free-kick from Bentley saw the Ghanaian fall onto the back post under pressure from Samba. After treatment he got back to his feet but then fell to the turf prompting the 'keeper to be stretchered off. Colin Doyle coming on to replace.

The pattern of play continued towards the Birmingham goal in the second half, five minutes after the restart Jason Roberts found him through on goal, but whilst his curled effort beat Doyle, the ball also flew the wrong side of the far post.

But in shooting goalwards, the former Wigan striker picked up an injury and had to be helped off the pitch to be replaced by Roque Santa Cruz.

It looked like Rovers were going to endure a night of frustration, Christopher Samba went on one of his trademark forward runs, he struck the ball well to the near post, Doyle spilled the shot, Derbyshire was there first for the rebound only to see the ball crash off the underside of the bar and away to safety.

But just as thoughts of extra-time started to enter the minds of fans and players, David Bentley struck with a sensational strike on 66 minutes to settle the nerves. Tugay fed the ball into Bentley, who, with his back to goal, ran into the space afforded to him before unleashing a shot from 25 yards that flew into the far corner of the net.

That prompted Birmingham to have their best spell of the game, former Rovers players Neil Danns and Damien Johnson both had efforts at goal, but neither troubled Brad Friedel.

But the play was quickly towards the Birmingham end, and finally they got the second goal. Matt Derbyshire bore down on goal only to find his route to goal blocked, wrestled to the ground, leaving referee Mike Riley no option but to point to the spot. It was the Blackburn-born striker who took the spot-kick, stroking the ball home into the bottom left corner of the net.

Just before the clocked ticked over to ninety minutes a third was added, it was Roque Santa Cruz who started the move, taking the ball before spreading it wide to Brett Emerton on the right, the Australian's cross took a deflection and that meant it was perfect for Santa Cruz who powered a header past Doyle into the net.

There was time for Doyle to deny Santa Cruz from adding to the goal count further, but a fourth would have been greedy as Rovers won with ease.

The draw for the last 16 of the competition takes place this Saturday lunchtime.

ROVERS: Friedel, Ooijer, Samba, Tugay, Emerton, Bentley, Mokoena, Dunn, Derbyshire (sub Rigters 83 mins), Olsson (sub Warnock 78 mins), Roberts (sub Santa Cruz 54 mins).

Subs not used: Brown, Khizanishvili.

BIRMINGHAM: Kingson (sub Doyle 45 mins), Sadler, Vine, O'Connor, Taylor, Johnson, Danns, Jaidi (sub Schmitz 56 mins), Forssell, De Ridder (sub Palacios 80 mins), Parnaby.

Subs not used: Pearce, Howland.

Booked: Jaidi (Birmingham)

Attendance: 9,205.