Something was amiss. He looked, in every sense of the word, nervous, the rarest of emotions for Phelps.
But minutes before the start of the 400-meter individual medley final, something unusual happened.
"I started getting these chills up my body," Phelps said. "Right then, I knew I was starting to get more and more excited."
The excitement translated into another historic performance by Phelps as the 23-year-old from Rodgers Forge won his first gold medal of the 2008 Olympics, dominating the race and setting a world record with a time of 4 minutes, 3.84 seconds.
It was an event that most expected would be one of his toughest races this week, but Phelps showed just how ready he is to chase history, blowing past Hungary's Laszlo Cseh and American Ryan Lochte. He now has one gold medal down, and seven to go as he takes his best shot at breaking Mark Spitz's record of seven, set at the 1972 Olympics in Munich, Germany. With four more wins, he'll hold the record for most gold medals first-place finishes by an Olympian.
Towson's Katie Hoff also grabbed a small piece of personal history, winning her first Olympic medal with a third-place finish in the women's 400-meter individual medley.
Hoff swam within a second of her personal best time, but Australia's Stephanie Rice was simply too strong and too fast, cruising to the gold and shaving more than two seconds off of Hoff's world record with a time of 4 minutes, 29.45 seconds. Zimbabwe's Kristy Coventry touched just ahead of Hoff to win the silver.
"It's my first Olympic medal, so I'm excited," Hoff said.
Phelps's race was close through the first 200 meters, which usually isn't a good sign for him. His breaststroke is the weakest of his four strokes, and typically in the individual medley, he needs to be leading going into that stage of race.
"At 1:50, I saw the clock and how tight we were together," said Phelps. "I thought this was going to be pretty painful, the last 200 [meters]. I knew the breaststroke was going to be the key to race, and I think that was my fastest breaststroke split ever."
Leading by half a body length going into the final 50 meters, Phelps shot off the final wall as if he'd been rocketed forward by a trampoline.
He increased his lead over Cseh and Lochte by a margin so overwhelming that he even allowed himself to get a little emotional over the final few meters. As he stroked toward the wall, he said he had something of an out-of-body experience, thinking back to his race in Athens, when he won his first gold medal.
"I remember coming off the last wall in Athens, and it was kind of the same feeling," Phelps said. "I saw myself out there. I sort of started smiling, and then I realized I was hurting and they could catch me if I didn't start moving."
After he finished, Phelps pumped his arms and scanned the crowd, trying to find his mother, Debbie, and his sisters Hillary and Whitney. He couldn't figure out where they were sitting, but he did make eye contact with President Bush, who was in attendance with his wife Laura, his daughter Barbara and his father, former President George H. W. Bush.
President Bush waved a tiny American flag, gave Phelps a thumbs-up, and then nodded to him after he climbed out of the pool.
"That's a pretty special feeling. I waved and nodded my head back. That's a pretty special to have the president here cheering you on," Phelps said.
On the medal podium, Phelps was uncharacteristically emotional, with his eyes welling up with tears during the national anthem. He wanted to sing along to the lyrics, but he was so overwhelmed by the moment that all he could do was grin.
"I couldn't stop crying," Phelps said. "I was just thinking about everything I've been through this year. It was just really emotional."