Jonny Marray and Frederik Nielsen could not extend their perfect record at the ATP World Tour Finals but still progressed to the semi-finals as Group B winners.
The Wimbledon champions suffered a 6-3 7-5 defeat to Robert Lindstedt and Horia Tecau at the O2 Arena but had already ensured they would top their group.
British player Marray and his Danish partner Nielsen had won their two opening games of the competition but could not recapture that form on Friday.
Sweden's Lindstedt and Tecau of Romania had no chance of making the semi-finals but gained a measure of revenge against the pair who beat them in the Wimbledon final.
Marray and Nielsen will find out who they will play in the semi-finals on Sunday when Group B is completed on Saturday.