RIO DE JANEIRO — Michael Phelps won a gold medal on Tuesday night, which is almost ordinary by now. It was his 20th Olympic gold.

His post-race performance, however, was something different.

After winning the 200-meter butterfly — his signature event — for the third time, Phelps stood triumphant in the pool, gesturing with bravado. He was stone-faced and silent, but his motions loudly said, “I’ll take all comers.”

“I was pretty fired up after that race,” Phelps said, adding, “I didn’t say anything to anybody else, but there wasn’t a shot in hell I was losing that tonight.”