Schalke striker Klaas-Jan Huntelaar returned to individual training on Tuesday in an effort to recover his full fitness before the end of the season.
The 29-year-old Netherlands international suffered a knee injury during the Royal Blues' 2-1 home win against Borussia Dortmund last month.
"It is a nice feeling to finally be back on the pitch," he told Schalke's official website. "The game against [Bayer] Leverkusen is too early for me.
"After that we have to see what is possible. I want to be playing as soon as possible and help the team.
"Those four weeks were a testing time for me. It is not a secret a footballer wants to play."
Schalke are currently fourth in the Bundesliga with 45 points from 28 matches.