Jack Draper's return from injury suffered another setback as he lost 6-3 7-5 to Martin Landaluce in the first round of the Cincinnati Open.
The former US Open semi-finalist, playing only his second match since missing Wimbledon, sent down 12 double faults and lost five consecutive games. He had been two breaks up in the second set before his level dropped.
After being given a wild card into the tournament, Draper struggled with fatigue beyond the 90-minute mark and bowed out after one hour and 57 minutes.
"The way I'm usually able to fight for every ball and conduct myself, it's just missing," Draper told reporters. "The level of my fall almost from where I was last year and the amount of things that I'm having to change in my tennis ... The mountain seems very, very big."
Draper, ranked 143rd, now faces a likely qualifying campaign for the US Open later this month.