JULIO Arca's desperation to play in last weekend's Tyne-Wear derby has spectacularly backfired and the skilful midfielder is now set for a lengthy spell on the sidelines.

The 24-year-old Argentinean originally suffered a metatarsal injury to his left foot during the Black Cats' 2-0 victory over North-East rivals Middlesbrough just over a month ago.

Arca was initially put in plaster to speed up his recovery and trained at the Academy of Light prior to the derby against Newcastle without any problems.

But it appears he aggravated the injury while appearing as a second half substitute.

Originally the Sunderland camp believed Arca had little more than a swollen toe, but a scan revealed that he has cracked a metatarsal bone.

England skipper David Beckham famously broke a metatarsal prior to the World Cup in Japan three-and-a-half years ago and spent six weeks on the sidelines.

Beckham's injury was not to his favoured right foot, however, whereas Arca's crack is on his preferred left foot.

An exasperated Mick McCarthy has now braced himself for a worst case scenario and fears he could be without his midfield maestro for anything up to eight weeks.

"There is no timescale on his return," said a frustrated McCarthy ahead of Portsmouth's visit to the Stadium of Light tomorrow.

"Perhaps in his haste to play against Newcastle and our desire to have him in the squad he has aggravated the injury.

"Perhaps in hindsight he shouldn't have been involved. Maybe then this week or next week he would have been all right. But that is 20-20 vision.

"He said he was fine before the game. He trained for two days and he was watched very closely. It was not just a case of saying he would play in the derby, he was fine and trained perfectly.

"If you a have sore toe, it is very difficult to run or kick the ball, especially as it's his left foot. Well let's face it his right foot is for just standing on. But he got clattered in the derby as soon as he came on."

The boss revealed his midfield playmaker can barely walk and has been consigned to the club gymnasium as part of his rehabilitation routine.

McCarthy added: "He can't do anything. He is just doing work in the gym. He can't put weight on his toe, although he can walk on it.

"But there is nothing he can do about it. He gets treatment off a machine that helps the healing of the toe.

"He has bone bruising and he has a crack on the inside of it. There is nothing we can do. We just have to let it heal."

It is beyond question that the Black Cats miss Arca's skill and guile when he is absent as he is the club's most creative player. Or, as Newcastle boss Graeme Souness would say: "he is one of the club's door openers".

His classy show at the Riverside against Middlesbrough last month provided overwhelming evidence of his worth to the Wearsiders' cause in their struggle to stop in the top flight this season - a fact not lost on the Sunderland manager.

"He is an important player for us," said McCarthy. "He was very instrumental last year and this season as well.

"He is a special player. He is technically gifted, he can find a pass or make a cross. We would like him back, of course."

Arca is not the only player likely to be missing for the visit of Alain Perrin's Pompey side tomorrow and McCarthy could have a defensive crisis on his hands .

Alan Stubbs is still suffering from a groin injury; skipper Gary Breen has a bruised rib and Danny Collins sustained a dead leg against Arsenal in the Carling Cup defeat to Arsenal on Tuesday.

Should all three fail to recover then the Black Cats boss will have little option but to recall Neill Collins back to Wearside from his loan spell at Hartlepool, where he has impressed in recent weeks.

Christain Bassila, George McCartney, Kevin Kyle, Matt Piper and Colin Healy also miss out.

Stephen Wright, meanwhile, will return to full-time training next week after recovering from long-term injury.

* Portsmouth have suffered a new blow ahead of their vital scrap at Sunderland with centre-back Andy O'Brien looking certain to be ruled out with a knee injury.

The Republic of Ireland defender, signed for £2m from Newcastle in the summer, could also miss the home clash with Wigan next week.

O'Brien has largely been a tower of strength in the Pompey defence this season, despite just one win in ten league games.

The 36-year-old took a knock in the 2-1 home defeat by Charlton and manager Alain Perrin said: ''On Wednesday we thought it would be fine but he came in the next day and it was not right.We would miss him because he has played well.''

Perrin, favourite to be the first Premiership manager sacked this season, has told his players to be brave and aim for six points from the next two games.

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