Phelps wins 100 butterfly in Arena Pro Swim Series

Updated Mar. 4, 2020 3:59 p.m. ET

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AUSTIN, Texas (AP) Michael Phelps was satisfied with one race Friday night but not the other.

Preparing for his fifth Olympics this summer in Rio, the 30-year-old Phelps won the 100-meter butterfly Friday night in an Arena Pro Swim Series event.

Phelps finished in 51.94. He won the gold medal in that event at the 2012 Olympics in London. He retired after London with 22 career medals, 18 of them gold, but returned to swimming in 2014.

Phelps was sixth in the 100 freestyle Friday, an event won by Nathan Adrian in 48.91. Adrian won the gold medal in the event in London.

''I thought I finished well in the 100 fly,'' Phelps said. ''My freestyle stroke isn't fully there, which is frustrating. Being a body-length behind at the 50, it's not really a place where you want to be. I didn't die. I finished well. I thought the last 10 meters of the 100 free were great.

''The biggest thing for tonight is I'm happy to be able to do that double and go 51.9.''

Adrian wasn't thrilled about his performance in 100 free.

''It's an OK race,'' Adrian said. ''It wasn't good. I really wish that was just a semifinal swim so I could come back tomorrow night and try to pull off a good one.''

Sarah Sjostrom of Sweden won the women's 100 free style and 100 butterfly in 53.12 and 56.38 respectively, both times the best ever in the United States.

''I couldn't have wished for a better start to the year,'' Sjostrom said. ''I'm very surprised with the times. It's fast this early in the year. I'm very happy to do those times.''

Katie Ledecky won the 400 freestyle in 3:59.54, the fifth-best time ever. Ledecky holds the world record and seven of the top eight times ever. The 18-year-old American won the 800 free style in London.

Earlier Friday, Ledecky was second behind Sjostrom in the 100 freestyle.

''It's a good night,'' Ledecky said. ''It was my first time going under four minutes with another event. I thought tha was really good coming off the 100.''