Bayer Leverkusen striker Stefan Kiessling sustained a hamstring problem in his team's 3-0 loss to Borussia Dortmund. The prolific hitman took a knock in the first half of Saturday's Bundesliga game, and was taken off as a result. The full extent of Kiessling's injury is yet to be determined. He is traveling to Munich on Monday to undergo medical tests. "It doesn't look good for Stefan. We fear that he has torn a muscle in his hamstring, but he has yet to undergo further examination," Leverkusen sporting director Rudi Voeller told Bild. Kiessling, 26, has scored 16 goals in 27 league appearances so far this season. Leverkusen's firepower is likely to be abysmally affected during his absence.