TONY Mowbray claims Middlesbrough are paying a heavy price for the absence of their key defenders, but admits he will have to name another patched-up back four when he takes his side to Burnley tomorrow.

With Justin Hoyte, Jonathan Woodgate and Seb Hines all unavailable, Mowbray was forced to play full-back George Friend at centre-half in Saturday's game at Crystal Palace, with winger Andy Halliday drafted into the left-back role.

The result was a thumping 4-1 defeat that means Boro have now lost six of their seven Championship matches since the turn of the year, a run that has raised serious doubts about their ability to remain in the promotion chase in the final two-and-a-half months of the season.

Alarmingly, they have conceded 11 goals in their last four matches, even though one of those games, against Leeds, featured a rare clean sheet.

Tonight's game at Burnley offers an opportunity to stabilise the club's position in the final play-off place, although Mowbray will once again be unable to call on the services of some of his most influential defenders. Indeed, with Stuart Parnaby having suffered a hamstring injury at Selhurst Park, things could be even worse at Turf Moor.

“It's becoming a concern,” said the Boro boss. “To lose three at Derby, four at Ipswich and then four again at Palace, it's a worry.

“Yet there are personnel reasons. I could give you our first-choice back four, and at the minute, you'd have to say that three of them aren't playing. That's football and you have to get on with it. The squad is only ever as strong or as weak as the numbers underneath what you would call the first XI. That's what football is.

“If we've got Hoyte, Woodgate and Hines injured, you have to take it on the chin and get on with it. Unfortunately, I don't think any of them will have a chance for Tuesday.”

The Boro back four was ripped apart repeatedly at Selhurst Park, and while Wilfried Zaha and the in-form Glenn Murray have been troubling Championship defences all season, the ease with which the duo carved the Teessiders open was a major source of alarm.

It is hard to imagine Mowbray starting with the same defensive unit tomorrow, so he could opt to move Rhys Williams into the back four instead of naming the Australian in midfield, as he did at the weekend.

The other option is to end Stephen McManus' exile from the first-team picture and accept that it might be better to field two natural centre-halves alongside each other rather than attempting to force a series of round pegs into a square hole.

McManus has only made one Championship start for Boro all season, but it came in a notable 2-1 away win at Watford, and after returning from a loan spell at Bristol City, the Scotsman was an unused substitute at the weekend.

“Stephen was at Palace sitting on the bench, so let's see what happens,” said Mowbray. “If we need Stephen, we'll have to do what we need to do. Centre-halves have got to play in their position, so if Stephen's required, he'll play.”

In truth, the identity of Boro's centre-halves will make no difference if Mowbray's players continue to make the kind of basic individual errors that have peppered their most recent displays.

Faris Haroun inexplicably failed to make contact with the ball as he attempted to clear in the build up to Palace's opening goal on Saturday, while Andre Bikey was turned much too easily as former Newcastle defender Peter Ramage doubled the Eagles' lead from a corner shortly after the interval.

“People make mistakes, but your team have to dig each other out,” said Mowbray. “You have to keep going, and once a mistake is made, somebody else has to react and stop a goal going in. I feel a bit as though that's not happening at the moment.

“The second goal was off a corner again, which takes us back to Ipswich (where Boro twice conceded from corners). Those things will kill you in the end, to the point where the game is over. If you lose direct goals like that off a corner, you can't win football matches. Even though you work hard on it on the training ground and everyone knows their job, if you give someone a job to do and they don't do it and someone scores, that's that.”