Newcastle United midfielder Kieron Dyer seems certain to miss this weekend's game with Birmingham City after he suffered a reaction to his hamstring injury on his return to first-team action.
A statement on the club's official website read: "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 to help him regain his full fitness."
The England international has suffered an ongoing problem with his hamstring which ruled him out at the end of last season.
A recurrence following the game with Manchester United at the start of the new campaign saw him sidelined since the end of August.
The 26-year-old returned to action last weekend when he came on as a substitute during the 3-0 win at West Bromwich Albion and set up the second goal for Michael Owen with a low cross from the right.
However, this was just a temporary respite.
Dyer has visited a number of experts in a bid to solve the problem, including the renowned Dr Hans Mueller-Wolfhart, who has treated the likes of double Olympic champion Kelly Holmes, and was told his persistent injuries could be the result of a back problem.
Michael Owen, Emre, Titus Bramble and Albert Luque have also suffered hamstring injuries this season, something which manager Graeme Souness put down to the Magpies' training ground prompting him to switch.
However, it appears Dyer's problems are far more deep rooted.
