SYDNEY -- Taylor Fritz and Madison Keys fueled a critical day for Team USA on Monday, posting victories over Germany at the United Cup mixed teams event, securing the Americans a berth in the tennis tournament's quarterfinals.
The competition vs. Germany continues Tuesday, when Jessica Pegula faces Laura Siegemund and Francis Tiafoe meets Oscar Otte. But based on points -- and Team USA's tournament-opening 4-1 victory over the Czech Republic -- the Americans have ensured a spot at the top of Group C, and will take on Great Britain on Wednesday for a right to advance to the event's final four.
Fritz took advantage of a dominant serve to defeat Alexander Zverev 6-1, 6-4 as the U.S. took a 1-0 lead. Keys doubled the advantage, orchestrating a 6-2, 6-3 win over Jule Niemeier, Keys' second victory of the season.
The ninth-ranked Fritz won 96% (26/27) of first-serve points and backed that up with accurate ball striking to beat No. 12 Zverev in just 64 minutes. He raced to an early lead, winning the first five games of the match as he stepped into the court to finish points set up by his serve.
From there, Fritz kept the pressure on against an overmatched Zverev, who was playing for only the second time since June when he damaged ligaments in his right ankle during his semifinal against Rafael Nadal at the French Open.
The 25-year-old Fritz is now 3-4 in head-to-head meetings with Zverev, and is 2-0 at the United Cup after defeating Jiri Lehecka of the Czech Republic in his opening match.
Keys' victory was comfortable as well, winning an elite clash of baseliners in just more than 70 minutes. Her power and pinpoint serving proved too much for the 23-year-old German, Niemeier.
While Keys served at 77% and lost just six points behind her first serve, Niemeier struggled with the rhythm of her serve and opened with three double faults to give her opponent an early break. Niemeier finished with seven double faults.
"I think overall I played really solid," Keys said. "I just tried to make as many first serves as possible to make things as easy as a tennis match could be."
The United Cup features 18 mixed teams competing over an 11-day stretch in three Australian cities. The final will be played Jan. 8 in Sydney.
The Associated Press contributed to this report.