The 32-year-old has scored six goals for the Potters this season, but has not found the back of the net since January 29.
The Stoke manager told reporters: "There's been a while, especially after his injury, where Peter has not performed to the level he was at before.
"He had a good start to the season and looked a real handful. Hopefully he will be back to what he was in the next five games."
The club is just three points clear of the Premier League relegation zone.