WASHINGTON -- A day before the Citi Open started, 2011 US Open champion Samantha Stosur spent an hour hitting on court with 173rd-ranked Jessica Pegula.
On Friday, in the hard-court tournament's quarterfinals, wild-card entry Pegula stunned the top-seeded Stosur 7-6 (4), 6-3 to get to a WTA semifinal for the first time.
Pegula, 22, said that spending time with Stosur before the tournament was a boost, because it gave a little insight into the sort of professionalism needed to reach the upper echelon of the tour.
"She probably doesn't want to hear that," Pegula said, "but it really helped me practicing with her."
Stosur led 4-1 in the opening tiebreaker before losing six consecutive points to drop that set.
The only break of the match came in the next-to-last-game, when Pegula went up 5-3, then served out what she called "probably the biggest win of my career."
Pegula, whose parents own the NFL's Buffalo Bills and NHL's Buffalo Sabres, had lost seven of her previous eight matches before arriving in Washington.
So her performance this week is "100 percent a step in the right direction," Pegula said. "I was losing to people ranked a lot lower than me. ... I was in a miserable mood."
On Saturday, she will face either Lauren Davis or Camila Giorgi for a berth in the final.
The other semifinal at the hard-court tournament will be No. 6-seeded Yulia Putintseva against No. 7 Yanina Wickmayer.
Wickmayer beat No. 4 Kristina Mladenovic 4-6, 6-3, 6-4, while Putintseva defeated Risa Ozaki 6-4, 6-2.