Just under 40 minutes after winning the 200-meter individual medley for his 22nd Olympic gold medal, Michael Phelps was back in the water for the semifinals of the 100m butterfly, an event he has won at the previous three Olympic Games.
The grueling double on Thursday appeared to take its toll on Phelps, who was last at the halfway point but battled back to advance to Friday's final despite being visibly tired the final 10 meters of the race as his arm tempo tightened up considerably.
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Phelps, who clocked in at 51.