Thomas Muller suffered a bruise thigh in Bayern Munich's DFB Pokal victory on Tuesday.
Muller was involved in a collision in the play that led to Bayern's opening goal, and though he tried to continue he was eventually replaced by Corentin Tolisso after 32 minutes.
Coach Jupp Heynckes said the substitution was only a precaution after Bayern's 6-0 quarterfinal win at Paderborn.
"Muller has a bruised thigh so we'll have to see how the injury develops over the next few days," he said. "He could have carried on, but was restricted and unable to give his maximum."
Kingsley Coman, Robert Lewandowski, Joshua Kimmich, Tolisso and Robben were on the scoresheet as Bayern advanced to the semifinals for a ninth consecutive year.
"Of course, everyone is delighted that we have qualified for the next round," Heynckes said. "We dealt with the difficult surface very well, scored wonderful goals and deserved the win."
Joshua Kimmich said the game was not as easy as the scoreline suggested, with the third-division hosts having a goal ruled out for offside, hitting the post and missing a tap-in.
"They played really bravely," he told Sky. "Huge compliments to Paderborn. They tried to play football on this surface."