Powell is one of the favourites for the 100m Olympic title
Asafa Powell's build-up to the Olympics has suffered a blow after he pulled up with a groin strain during a 100m race at Rome's Golden Gala.
Despite pulling up towards the end of the heat, the former world record holder still finished in a time of 10.19 seconds to qualify for the final.
"He just felt his groin cramp up," said manager Paul Doyle.
"He's not going to take any chances in an Olympic year. He's had groin problems before and got over them."
Powell, who did not run the final as a result, is one of the favourites for the Olympic 100m title but lost to Usain Bolt at the recent Jamaican Olympic trials last month and saw his compatriot steal his world record in May by running 9.72.
His injury comes a week after rival and world champion Tyson Gay suffered a muscle strain in the US trials which meant him failing to qualify for the 200m in Beijing.
In Powell's absence, defending Olympic silver medalist Francis Obikwelu won the 100m in Rome.
Olympic and world champion Jeremy Wariner turned the tables on compatriot LaShawn Merritt, who beat him at the US trials, to win the 400m in a photo finish.
Wariner won in 44.36 seconds - one-hundredth ahead of Merritt.
"I got out strong. I worked my tires. I finally executed like I should have at the trials," Wariner said.
Double-amputee sprinter Oscar Pistorius missed out on his second attempt to qualify for the Olympics.
The South African ran 46.62 seconds to finish seventh in the 400m B race, but needs to run 45.55 to qualify for the individual event in Beijing, or the B qualifying time of 45.95 for a possible relay spot.
The 21-year-old, whose personal best is 46.36, did improve on his 47.78 effort in Milan last week, his first run since overturning a ban on him competing against able-bodied athletes at the Court of Arbitration for Sport (CAS) in May.
"With the amount of training I've had I'm not too disappointed," Pistorius said.
"I've got a third chance coming up in Switzerland in five days. Regardless of qualification, I'm happy with the time."
Pistorius will have a final qualifying attempt in Lucerne on 16 July.