Andy Roddick's U.S. Open preparations have taken a turn for the worst after suffering a back injury in a first round defeat by France's Jeremy Chardy at the Cincinnati tennis Open.
The American struggled in the second set during which he had treatment for back spasms.
After receiving attention, Roddick's serve was noticeably slower and he was broken twice by the Frenchman who is ranked 38th in the world.
Tournament wins in Atlanta and Eastbourne had indicated an upturn in form for Roddick but now he has to see whether he will be fit to play at Winston-Salem next week or hold himself back for the Open at the end of the month.
Chardy will take on Russia's Denis Istomin in the second round.