Roger Federer's 21-year run with Nike is over.

Federer walked out on Centre Court for his Wimbledon opener on Monday in a white Uniqlo shirt, wristband and headband.

His most recent contract with Nike expired in March, and he had been rumored to be considering a switch. It became public when he stepped out at the All England Club.

Signing Federer is a coup for Uniqlo, a Japanese brand that has made inroads in the United States since opening its first store in 2006. Uniqlo is known for its low-cost, no-frills casual clothes.

Nike has a stable of other star athlete sponsors, including LeBron James and Serena Williams. But few have become as closely linked to the brand as the 36-year-old Swiss tennis legend. Federer, the men's top seed at Wimbledon, is seeking to add to his men's record 20 grand slam titles.

"He had become one of their marquee endorsers. He was at that top tier," said Jim Andrews, a sponsorship expert with research firm IEG.

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Nike said in a regulatory filing last year that "investments in endorsements by high-profile athletes, sports teams and leagues" helped drive sales up 6% to $34.4 billion.

It's not clear whether Nike will continue to market or sell its trademark Federer shoe and clothing line with his initials. Federer wore Nike shoes for the Wimbledon opener, and may continue to because Uniqlo doesn't make tennis shoes.

"I assume that the RF line that we've come to know will simply go away," Andrews said.

Federer will immediately become the face of Uniqlo. Golfer Adam Scott and tennis star Kei Nishikori were its best known endorsers until Monday.

Uniqlo tweeted a photo of Federer shortly after he headed out for the match.

"I was excited to wear Uniqlo today, I must tell you," Federer said after his victory in straight sets. "It's been a long time coming."

The company did not disclose terms of the deal, but ESPN reported it was worth $300 million for 10 years. Nike reportedly paid Federer $10 million a year beginning in 2008.

"Uniqlo really said, 'We need to make a major move within tennis,'" Andrews said. It had a deal with Novak Djokovic beginning in 2012, but he left for Lacoste last year.