NBC Olympics.com – Michael Phelps swam the 100m butterfly preliminary heats on Thursday afternoon, admitting that he "screwed up" the race in a pool-side interview. Instead of advancing to the second semifinal – which he could have done if he had swum just a hair slower – where he would buy himself eight or so extra precious minutes after he races in the critical 200m individual medley final on Thursday night, he'll be in the first one. And potentially more tired on quest for four-peat, as he won the 100m butterfly in the 2004, 2008 and 2012 Olympics.
Phelps raced to 51.60 seconds, good enough for fourth place overall. U.S. teammate Tom Shields, making his Olympic debut, clocked 51.58 and will also advance.