Liverpool plan a total overhaul of Fernando Torres's medical care to try to discover the reason for his fifth hamstring injury in 16 months.
The Spanish striker broke down again during Wednesday's Champions League victory over Marseille.
Scans have revealed a repetition of the injury that could rule him out for three weeks, the December 21 trip to Arsenal being the tentative target for his comeback.
Torres has had three similar injuries on international duty, and two now with Liverpool, in the 16 months since his arrival at Anfield from Atletico Madrid.
Boss Rafael Benitez reveals Torres has no history of such an injury in Spain, which further deepens the concerns over his fitness.
He said: "Fernando had no such muscle or hamstring problems while with Atletico Madrid."
But as former Liverpool star Michael Owen knows all too well, hamstring injuries can dog you for the rest of your career once they have taken hold.
And now the 24-year-old striker has voiced his own concerns at the problem. He said: "I am a little disappointed, but all I can do is move forward.
"It is worrying me because it has happened a few times. After this latest injury the important thing is to recover without rushing a comeback date and trying to make sure it does not happen again."
Torres will miss Monday's game at home to West Ham, and could also be sidelined for matches against Blackburn, PSV Eindhoven and Hull.
Benitez said: "We are very disappointed with the situation. We have to analyse why it has happened. We have been working with prevention exercises in the past, and still we have the same problem.
"We were taking time with him, he wasn't being rushed back. The time and training was all under control, as was all the exercises.
"We now have to analyse why it has happened again. The doctor and the physio were both working very hard with Fernando and they are both first-class, but now it is the same situation.
"We will now not be taking any risks with his comeback. If he is fit then he will play, if he is not fit then he won't, it is simple."
He added: "We were working very hard with prevention exercises, and that was after the first couple of times that it happened.
"But it has happened again. He played in the Carling Cup and was not sharp, but he was sharp in training and little by little he was put under pressure."
Torres had short spells against West Brom, Tottenham and Bolton, plus a substitute appearance for Spain against Chile. Then he played two full games and broke down again.
Benitez said: "Everything was under control. But maybe against Marseille he was tired towards the end of the match and that is when it happened again. He went on a sprint and pulled something.
"Now we will have to start all over again to try to solve this problem.
"Because it has happened again and again we must analyse the small things. Maybe the way you walk, maybe your footwear or the exercises you do.
"I have talked to Fernando looking for a solution, and also with the doctor and physio staff. We must solve this, it is not a serious injury, more one that is difficult to cure."
Robbie Keane will now get an extended opportunity to stake a claim for a regular place, having been substitute against Marseille to facilitate Torres' comeback.
Liverpool have also lost full-back Fabio Aurelio with a calf injury, and Italian defender Andreas Dossena should step in against the Hammers.