Wolfsburg winger Vieirinha could miss several months of the season after rupturing ligaments in his knee during their 2-0 win over 2. Bundesliga side Aalen in the DFB-Pokal on Tuesday night.
The Portuguese, who was stretchered off in the 31st minute, has vowed to return as quickly as possible from the injury.
"It's a very difficult moment but I know my family, my team-mates and our supporters will give me the support to come back quickly," FIFA.com quotes him as saying.
The club's director of football Klaus Allofs has admitted that the injury was a big blow for Wolfsburg.
"It's cruel for him and for us," Allofs said. "We all wish him a speedy recovery and will do everything possible to help with the rehabilitation."
Vieirinha joined Wolfsburg last summer from PAOK.