Mick McCarthy is likely to give full international debuts to Everton's Richard Dunne and Andy O'Brien of Bradford City before the summer, but the Republic of Ireland manager insists that despite the continued experimentation he is not looking to replace Gary Breen as Kenny Cunningham's regular partner in the centre of Ireland's defence.

In the wake of Wednesday's win against the Czech Republic McCarthy admits that he will continue to review his options in what is widely seen as a problem position. But he maintains that Breen, who has 26 caps, remains his first choice with Cunningham for the World Cup qualifying campaign.

"Kenny would be my choice to play alongside any of them," he said yesterday, "but the pairing of himself and Gary playing together has been a different class for me over the last few years and I wouldn't see any reason to go changing it."

With Breen's first-team place at Coventry under renewed pressure this week following the arrival from Rangers of Colin Hendry at Highfield Road, though, McCarthy's attempt to broaden his options has been given some added urgency.

Against the Czechs Paul Butler struggled to adapt to the situation while Phil Babb coasted fairly impressively through a second half in which the Irish defence were under far less pressure than they had been in the first.

Butler, who McCarthy insists can do far better than he did on his debut, will probably get another chance to show that he can successfully make the transition from club football while Babb's display, after a month of playing for Tranmere's first team, appears to have reinforced McCarthy's conviction that the 29-year-old has to be playing regularly in order to regain his form.

"It was a terrible night for big Paul to make his debut and he probably could have had it a lot easier than to be making it against the Czechs. He was a bag of nerves going out there beforehand, but it impressed me the way he tried to deal with the situation and while he did have a difficult time I know he can do better."

Butler, however, may well have slipped behind Dunne and O'Brien in the pecking order, with the younger pair both performing solidly in Tuesday's under-21 match at Belfield. However, some evidence of their inexperience was obvious in that game too and neither was around to prevent Milan Baros scoring a rather similar goal to the one by Jan Koller for which Butler took a large portion of the blame.

Both also seem to fall into the same category as Breen and Babb as players who can play well enough for the bulk of a game only to make a costly error. As such it's not entirely clear whether either can hope to make the step up from the under-21 team at this stage.

"From my point of view I thought they were good on Tuesday, I think Paul will do a lot better for us and I felt Phil was outstanding in the second half against the Czechs but needs to be playing regularly which he will be after the summer.

"All I'm attempting to do, though, is have a look at a few people in a position in which we probably haven't had the same sort of competition that there's been elsewhere. These lads are all playing Premiership football, they're playing good stuff, so it's not as if I'm chucking lads in from the second division or something.

"There could be injuries or other problems and it would be remiss of me not to have checked out every option available to me before we start off on the qualifiers."

Still, McCarthy must be hoping that one of the other players emerges as a more serious rival to Breen in the six friendlies that are scheduled to be played before the start of the World Cup campaign.

When the Czechs used their pace to run at the Irish defence on Wednesday there were times when the home side looked terribly exposed in the centre. By the autumn when Ireland visit the Netherlands and Portugal, McCarthy's central defence will have to be able to withstand a great deal of pressure as the Dutch and the Portuguese are likely to move the ball forward even more quickly than this week's visitors.

The upshot is that even after the boost of this week's win, McCarthy's side may well remain as vulnerable in this area during the next campaign as they were during the one just finished.