Schalke coach Huub Stevens has revealed that striker Raul has been playing through the pain barrier recently to help the club.
Raul lasted 70 minutes of Thursday night's Europa League 1-1 draw against Plzen before Stevens decided the risk was too great and withdrew the former Real Madrid man.
"He told me that he wanted to grit his teeth for the sake of the team, but after 70 minutes, I thought enough was enough," said Stevens.
"He is still suffering with a thigh injury and it is still causing him problems but we have another game on Sunday and I hope that he is fresh and fit to play against Wolfsburg."
Stevens was nevertheless satisfied with the result in the Czech Republic which gives the Bundesliga side a good chance of reaching the last 16.
"We have got to be happy because 1-1 away from home is a good result," Stevens said on his club's website.