Olympic 100m breaststroke champion Cameron Van der Burgh on Tuesday said he needed treatment on a shoulder injury after claiming the silver medal in the same event at the world championships.
The South African cruised into the final of the 50m breaststroke with the fastest time from Tuesday morning's heats but said he needed injections after being pipped to gold by Australia's Christian Sprenger.
"My shoulder flared up a little bit and we did a lot of needles last night but the knee is doing OK, so we're just trying to manage it," said Van der Burgh, whose season has been plagued by injury problems.
I think you can expect a world record from Cameron tomorrow
"Just like in the 100m breast, I'm just trying to make it from heats to the semi-final and to the final but it only counts in the final, as we've all seen, so I'm just trying to keep the best till last."
Despite his fitness concerns, Van der Burgh's South African team-mate Giulio Zorzi believes he could even threaten his own world record from four years ago in the final on Wednesday night.
"I think you can expect a world record from Cameron tomorrow," Zorzi said after also qualifying for Tuesday night's semi-finals.
"He's not in the same shape as he was last year for the 100m, but for the 50m he is definitely capable of it."
Van der Burgh himself acknowledged that despite his Olympic success over two lengths, the 50m that remained his favoured distance.
"I'm better suited to the 50m. I've always said that the 100m is my mistress that I cheat on the 50 with!
"She's always good to me and I always come back to her. The 50m is where I started and it's always fun to swim it."