Cincinnati - Andy Murray's comeback was sidetracked on Monday as the three-time Grand Slam champion lost 6-1, 1-6, 6-4 to Lucas Pouille in his opening match at the Cincinnati Masters.
Murray, returning from January hip surgery, was unable to get past the French 16th seed, hampering his preparations for the US Open starting on August 27.
Murray last played 11 days ago in a Washington third-round match which took him three hours to win and ended at 03:00.
The 31-year-old two-time Wimbledon winner is working his way back slowly and felt he could not subject his body to a quarter-final just over 12 hours later, prompting him to withdraw from that event.
Pouille had lost his previous three matches to Murray, the last at Dubai in 2017.
Murray, playing as a wildcard at an event he won in 2008 and 2011, saved a match point in the penultimate game on his serve and another moments later when Pouille was serving for the win.
But the Frenchman, who produced 40 winners to just 15 from Murray, closed it out at the third attempt.
Spanish 13th seed Pablo Carreno Busta started his week with a 6-3, 2-6, 6-3 defeat of France's Richard Gasquet, while Japan's Kei Nishikori put out Russian Andrey Rublev, 7-5, 6-3.
Peter Gojowczyk of Germany defeated Joao Sousa 2-6, 6-4, 7-5.
Results from the ATP and WTA Cincinnati Masters tournament on Monday (x denotes seeding):
Pablo Carreno Busta (ESP x13) bt Richard Gasquet (FRA) 6-3, 2-6, 6-3
Kei Nishikori (JPN) bt Andrey Rublev (RUS) 7-5, 6-3
Lucas Pouille (FRA x16) bt Andy Murray (GBR) 6-1, 1-6, 6-4
Peter Gojowczyk (GER) bt Joao Sousa (POR) 2-6, 6-4, 7-5
Denis Shapovalov (CAN) bt Frances Tiafoe (USA) 7-6 (8/6), 3-6, 7-5
Bradley Klahn (USA) bt Maximilian Marterer (GER) 7-6 (7/1), 6-4
Jerrmy Chardy (FRA) bt Fernando Verdasco (ESP) 6-1, 6-2
Benoit Paire (FRA) bt David Ferrer (ESP) 6-2, 6-2
Leonardo Mayer (ARG) bt Michael Mmoh (USA) 6-4, 1-6, 6-4
Sam Querrey (USA) bt John Isner (USA x9) 6-4, 6-7 (5/7), 7-6 (7/5)
Novak Djokovic (SRB x10) bt Steve Johnson (USA) 6-4, 7-6 (7/4)
Stan Wawrinka (SUI) bt Diego Schwartzman (ARG x12) 6-2, 4-6, 6-3
Lesia Tsurenko (UKR) bt Danielle Collins (USA) 6-0, 6-2
Victoria Azarenka (BLR) bt Carla Suarez Navarro (ESP) 6-7 (5/7), 6-2, 6-4
Viktoria Kuzmova (SVK) bt Aliaksandra Sasnovich (BLR) 6-0, 4-6, 6-1
Svetlana Kuznetsova (RUS) bt Stefanie Voegele (SUI) 6-4, 2-6, 7-6 (7/5)
Anett Kontaveit (EST) bt Barbora Strycova (CZE) 6-3, 6-0
Madison Keys (USA x13) bt Bethanie Mattek-Sands (USA) 3-6, 7-6 (7/3), 6-4
Kristina Mladenovic (FRA) bt Julia Goerges (GER x10) 6-4, 3-2 retired
Serena Williams (USA) bt Daria Gavrilova (AUS) 6-1, 6-2
Aryna Sabalenka (BLR) bt Johanna Konta (GBR) 4-6, 6-3, 6-4
Ajla Tomljanovic (AUS) bt Irina Begu (ROU) 4-6, 6-3, 6-3
Rebecca Peterson (SWE) bt Katerina Siniakov (CZE) 2-6, 6-4, 6-1
Alize Cornet (FRA) bt Jelena Ostapenko (LAT x11) 1-6, 7-5, 6-0