LONDON >> Manteo Mitchell heard the POP! and knew it wasn’t good. "It felt like somebody literally just snapped my leg in half," he said.

The American sprinter had 200 meters to go in the first leg of the 4×400-meter relay preliminaries Thursday and a decision to make: keep running or stop and lose the race. To him, it was never much of a choice.

He finished the lap and limped to the side to watch the Americans finish the race and qualify easily for the final. A few hours later, doctors confirmed what he suspected: He had run the last half-lap with a broken left fibula.

"I heard it and I felt it," Mitchell said. "But I figured it’s what almost any person would’ve done in that situation."

Mitchell finished in a more-than-respectable 46.1 seconds, and the United States tied the Bahamas in the second heat in 2 minutes, 58.87 seconds — the fastest time ever in the first round of the relay at the Olympics.

The 25-year-old sprinter from Cullowhee, N.C., said he was diagnosed with a complete break of the left fibula — but it was not a compound fracture and the bone is expected to heal on its own in four to six weeks.

The Americans have won gold in the past eight long relays they’ve entered at the Olympics.

"Even though track is an individual sport, you’ve got three guys depending on you, the whole world watching you," Mitchell said. "You don’t want to let anyone down."