Chelsea midfielder Michael Ballack will undergo more surgery on his troublesome ankle in Germany on Tuesday.
Ballack has not played since limping off against Newcastle in April
Problems developed after the Germany captain's initial operation at the start of May, and it is not known when he will be fit to start training again.
A statement on Chelsea's website said: "The operation is related only to a complication in the healing of the wound from previous surgery."
Ballack, 30, could miss the club's tour of America which starts on 10 July.
The Blues' first game in the US is against Club America at the Stanford Stadium on 14 July.
Chelsea then take part in a friendly tournament which sees them take on Suwon Bluewings on 17 July and LA Galaxy, David Beckham's new side, on 21 July.
Ballack first injured his ankle in a game against Newcastle on 22 April.
He has not played since and missed Chelsea's win over Manchester United in the FA Cup final and two Euro 2008 qualifiers in June.
Ballack moved to Stamford Bridge on a free transfer from Bayern Munich in May 2006.