DELRAY BEACH, Fla. (AP) Frances Tiafoe advanced to his first ATP Tour quarterfinal this year by beating fellow American Tommy Paul 7-5, 7-6 (4) on Thursday at the Delray Beach Open.

Tiafoe, the 2018 champion, said he was pleased to win playing less than his best.

''It seems like on tour I've only been able to win matches when I'm playing absolutely absurd tennis,'' he said. ''You're not going to feel amazing every match.''

In another all-American matchup, Steve Johnson beat wild card Jack Sock 6-4, 5-7, 6-1.

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