KIERON DYER has suffered yet another injury setback as the bulk of his Newcastle career continues to be spent on the sidelines.

Despite making a brief reappearance on Sunday, the club revealed yesterday that Dyer, who signed a new four-year deal in the summer, has suffered more woe .

St James' Park officials would not reveal the seriousness of the England midfielder's on-going problem but it is understood to be a medical condition, unrelated to his previous injuries, which is hampering his bid to regain full fitness after a long-standing hamstring complaint.

Dyer, whose medication is believed to be exacerbating the problem, has made just three appearances for the Magpies this season as attempts to cure the hamstring niggle have proved unsuccesful.

The last of those was a 20-minute cameo role against West Brom on Sunday after manager Graeme Souness decided to test the player out in a match situation.

Dyer - said to be close to tears after learning of his latest heartache - has already been to see renowned muscle and bone specialist Dr Hans Mueller-Wolfhart, while he more recently went to see a top Nottingham consultant.

But still there has been no solution to his hamstring injury and no timescale has been put on his return to the Premiership stage.

Yesterday a club statement revealed: "Kieron Dyer has a medical problem which has contributed to his lack of fitness. Unfortunately, he has suffered another reaction following his appearance last weekend and will require further specialist attention."

It was only last week, ahead of Newcastle's date with Grimsby in the Carling Cup, that manager Souness had spoken of his belief they had solved the hamstring injury once and for all. During six years on Tyneside Dyer has still to reach the 150 appearance milestone.

* Portsmouth rebel Laurent Robert will have to wait to regain his place in the team as manager Alain Perrin prepares to name an unchanged side for Saturday's Fratton Park clash with surprise package Wigan.

Robert left Pompey with only four substitutes after telling Perrin he was not fit enough to sit on the bench at Sunderland last weekend after he was left out of the starting line-up.

Yet Perrin's team stormed to a crucial 4-1 win against their relegation rivals at the Stadium of Light - with Matthew Taylor, playing in Robert's left-midfield role, scoring twice.

Robert, on loan from Newcastle, where he was involved in a number of spats with managers Sir Bobby Robson and Graeme Souness, made a grovelling apology to the Portsmouth board, Perrin and the fans. And he was fined two weeks wages, nearly £50,000.

He insisted he did have a groin injury and flew to Paris to see a specialist on Sunday, but Perrin said: ''Although he has looked bright in training this week it is difficult for me to change the team after a win like that. We scored four goals and played really well."

Read more about Newcastle United FC here.