Stan Wawrinka lost to Spanish left-hander Fernando Verdasco 6-2, 7-6 (3) in the first round at Queen's Club on Tuesday.
Wawrinka, seeded No. 2, is working with 1996 Wimbledon champion Richard Krajicek during the grass-court season, and their partnership got off to a rocky start as Verdasco broke serve in the opening game and took control of the set with a second break to lead 4-1.
In a match that was delayed and then interrupted by rain, the second set went with serve until Verdasco clinched victory in the tiebreaker.
Only two of 16 matches have so far been completed in the first two days of the Wimbledon warmup.