ALAN Shearer set out yesterday on his mission to beat a comeback target set by Newcastle United manager Bobby Robson.

The United boss and medical experts expect Shearer to be out for three months following surgery on his knee injury.

But Shearer hopes to be back sooner - and the derby at Middlesbrough on March 17 is in his sights.

Shearer checked in for the operation on his tendinitis problem on Wednesday and left hospital later the same day.

He was on crutches yesterday, but has already started fitness work in a bid to speed his recovery.

A club official confirmed yesterday that the surgery was successful.

"Alan was in and out in a day," she said. "He came out on crutches and his rehabilitation starts immediately. He will be out for approximately three months."

An earlier return is earmarked for defender Nikos Dabizas, who damaged knee ligaments in the second game of the season.

The Greek international plans to be back in training in the next month and could be playing before the end of February.

Dabizas has spent most of his time under the supervision of a specialist in Greece since an operation to repair the ruptured cruciate.

He has done fitness work for at least three hours a day and Newcastle's backroom staff are delighted with his progress.

Dabizas said: "The knee will be totally all right when I come back. The operation has been a complete success and I feel good mentally and physically."

Meanwhile, teenager Shola Ameobi faces an anxious wait before finding out whether he will face champions Manchester United tormorrow.

Manager Bobby Robson hinted he might rest Ameobi, who starred when he replaced Shearer in United's win against Leeds.

But it's now likely that Robson will stick with the lanky youngster, who posed problems for Rio Ferdinand and Jonathan Southgate,

Stand-in skipper Warren Barton is tipping the African-born striker as a star of the future and believes he can soften the disappointment of losing Shearer.

"It's a big blow to be without Alan, but we have to work hard to make up for his absence. As a squad, we believe in ourselves," said Barton.

Robson has no new injury problems as United prepare to face a team beaten 3-0 at St James's Park last season.

Shay Given could be fit again after having treatment on a leg injury which kept him out against Leeds, but is unlikely to displace Steve Harper.

Defender Alain Goma is also ready to make a comeback after a lengthy absence because of a calf strain, but Kevin Gallacher is losing his fight to be included