Liverpool manager Jurgen Klopp has told Daniel Sturridge that he needs to learn the difference between pain and "serious" pain following the striker's latest injury setback.
The England international was expected to be in the squad for Thursday night's 2-1 victory over Bordeaux, but pulled out just a few hours before the Europa League game at Anfield.
The 26-year-old, who recently recovered from a knee injury, is said to have suffered a foot problem.
"The situation is Daniel was very often injured in the last few months, and maybe years, so it is normal when you get back in training usually it is not the same quality, but you need training," Klopp told reporters. "Your body has to learn to adapt to new intensities of training and in this time you have to learn what is serious pain and what is only pain.
"Everyone wants him back on the pitch but we all have to learn. Now we can say [his latest issue] is not that serious but it is not possible to go on as before so we have to react to every situation, which is normal for injuries.
"When Daniel comes back usually after this long break you would train five weeks in a row and play only in friendly games. That would be the best, but of course we know the world is not perfect so we have to try the best and the quickest. It is a really long period so now we have to stay patient I am sorry to say - sorry for you, sorry for me, sorry for him."
Sturridge underwent surgery on his hip towards the end of last season.
