Skipper Gareth Southgate is facing a fight to be fit for Middlesbrough's triple cup test against Arsenal.
Southgate is suffering from hamstring trouble and was last night scheduled for a hospital scan to identify the problem.
Boro face Leicester tomorrow then meet the Gunners three times in nine days in the two-leg Carling Cup semi-final and the fourth round of the FA Cup.
The 33-year-old defender has been struggling with back trouble in recent weeks and limped out of training yesterday.
But manager Steve McClaren believes he will recover: "It's not a strain or a pull so we're hoping he will be OK," he revealed.
"He's had this for a while and his back's a bit niggly but we're looking to get him right for Saturday and Tuesday.
"Obviously it's very important for us to have him in these games and we'll do everything we can to make that happen."
Southgate's centre-back partner Ugo Ehiogu is aiming to be available to face Leicester at the Riverside after limping out of the 4-1 defeat at Highbury last Saturday with a groin problem.
Ehiogu was back in training yesterday and is likely to be in the squad, with Chris Riggott and Colin Cooper on stand-by.
Ehiogu, whose current contract runs out in 18 months, is in talks with the club over a new deal.
Danny Mills is ready to make his loan switch permanent if Boro can push it through with Leeds, though other clubs are interested.
Birmingham City also want the right back but he said: "I'm hearing Middlesbrough are making efforts to make it permanent, but that's out of my hands.
"I know there are one or two other clubs interested but I've just go to keep my head down and play well.
"I'm pleased with the way it's gone here. The fans here know I give it my best and I'll do that even if Middlesbrough do not make it permanent."
Boro's long-running legal dispute with Premiership rivals Liverpool over the transfer of full-back Christian Ziege will come to trial on March 22.
Boro are claiming multi-million pound damages, alleging the May 2000 transfer of German international Ziege - now at Tottenham Hotspur - was a breach of Premier League rules.
Ziege was sold to Liverpool for £5.5m after they became aware that he had a clause in his contract allowing him to leave Teesside if an offer of that value was made. But Boro claim his true value was £7.5m.
They also say his departure forced the team - then managed by Bryan Robson - to be reorganised, and cost them marketing and business opportunities.
In May 2002 Middlesbrough's case appeared to have been dealt a fatal blow when it was struck out by a High Court judge, but they successfully challenged his decision at the Court of Appeal.
The trial will last ten days, and will see big names from both clubs - including Liverpool manager Gerard Houllier and chief executive Rick Parry, as well as Ziege himself - taking the stand.
* Boro keeper Mark Schwarzer will be presented with a piece of crystal by Steve McClaren tomorrow in recognition of reaching 250 appearances for the club.
He is only the 46th player in the club's 128-year history to make 250 first team appearances.
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