NEW YORK -- Could Serena Williams have been key to Grigor Dimitrov’s fourth-round victory at the US Open against Andrey Rublev?

Dimitrov revealed he spoke to Williams, the six-time US Open singles champion, Saturday before triumphing in five sets Sunday. Dimitrov, 33, also discussed to what extent he gets nervous playing in front of his longtime friend.

“For some reason not in front of her,” Dimitrov said. “She gave me a good pep talk yesterday. Yep, I know, exactly. I’m thrilled.”

Must See

Williams was watching from a suite alongside American singer Alicia Keys.

“It’s amazing honestly to play in front of you guys, in front of good friends and family,” Dimitrov said. “All in all, it’s a tremendous atmosphere so again thank you all. Thank you so much for the support.”

Dimitrov will play Alexei Popyrin or Frances Tiafoe for a place in the semifinals at Flushing Meadows.