Michael Phelps has admitted that his opponents were "more prepared" than he was during the 400m individual medley.
The 27-year-old failed to claim a medal in the race, with his American teammate Ryan Lochte winning gold ahead of Thiago Pereira and Kosuke Hagino.
Phelps said: "Just a crappy race.
"I felt fine for the first 200m. I couldn't really go in the last 100m. I saw Thiago out there and they just swam a better race than me, swam a smarter race than me and were more prepared.
"That's why they're on the medal stand. I don't think the lane has anything to do with it."
Phelps will have six more chances to add to his record of 14 Olympic gold medals before the completion of the games.
