Russia's Igor Andreev retired from his second-round match against Gael Monfils at the Madrid Open on Wednesday.
Andreev was a set and a game down to the Frenchman when he decided he could not continue.
Monfils takes on No. 6 seed Tomas Berdych in the next round.
World No. 77 Andreev had upset 49th-ranked Juan Carlos Ferrero of Spain in the first round 6-4, 7-6 (4).
Andreev's season had looked to be picking up after a poor start that saw him fail to qualify for the Australian Open, get dumped out of the second round in Barcelona, and crash out of the first round at Estoril, Portugal last week.
He has three career titles and a top ranking of 18, reached in November 2008.
