Roger Federer relied on his trusted serve to beat Stefanos Tsitsipas 7-6 (5), 7-6 (4) on Thursday and give defending champion Switzerland a spot in the Hopman Cup final.
The victory assured Switzerland's advancement, but Greece claimed a consolation 2-1 victory when Maria Sakkari beat Belinda Bencic 6-3, 6-4 in women's singles.
Greece also won the mixed doubles 4-3 (4), 2-4, 4-3 (3) in the Fast4 format.
The 37-year-old Federer's precision went up against Tsitsipas' power in the first set of the men's singles match, and not much separated the two. Eight games were held at love.
"There was very little unforced errors and it was really good quality tennis," Federer said. "It could have easily gone three sets. For me it is about maintaining a good level of play and I am happy with my game."
Federer will be going for a record third Hopman Cup title when the Swiss team faces either host Australia or Germany in Saturday's final.
"I will be excited to watch it tomorrow and see who we play in the final," Federer said. "This format lends itself to some exciting tennis."
Federer lost only seven games in wins over Cameron Norrie and Frances Tiafoe but found it tougher in his first match against Tsitsipas.
Federer trailed 4-1 in the first tiebreaker before reeling off consecutive forehand winners to claw back into it. Tsitsipas double-faulted at 5-5 and Federer then won the set with an ace.
The serve continued to dictate play until Federer had break points in the ninth and 11th games but was unable to convert. The 23-time Grand Slam champion, however, raised his game in the tiebreaker with a perfect drop shot to take a 6-3 lead. He closed it out shortly after.
Federer's appearances at the past two Hopman Cups were followed by Australian Open titles.
Earlier, Serena Williams beat Katie Boulter 6-1, 7-6 (2) to complete an unbeaten Hopman Cup campaign in singles. With daughter Alexis Olympia in attendance, Williams was made to work in the second set before prevailing.
The winless United States, however, lost to Britain 2-1. Norrie upset Tiafoe 7-6 (4), 6-0 in men's singles and Britain won the mixed doubles 3-4 (2), 4-3 (4), 4-1.
The 37-year-old Williams' hopes for a record third Hopman Cup title ended when the United States was eliminated after losses to Greece and Switzerland.
Williams has slowly built momentum in her first tournament since the US Open in September as she eyes a record-equaling 24th Grand Slam singles title in Melbourne.
"It was definitely good to play three singles matches here, and the mixed (doubles)," Williams said on-court after her singles match.
Coach's words inspire Osaka
Naomi Osaka called in her coach for advice on how to swing momentum after losing the first set to Anastasija Sevastova, and it did the trick.
The US Open champion responded by conceding only five points in the next set on her way to a 3-6, 6-0, 6-4 win Thursday that secured her spot in the Brisbane International semifinals.
Kei Nishikori worked his own way out of a jam against 2017 champion Grigor Dimitrov when he was down a break in the second set of their quarterfinal match, winning six of the last seven games to clinch it 7-5, 7-5.
And so after the back-to-back matches on Pat Rafter Arena, two players from Japan, both seeded No 2, were into the semifinals.
Bajin, a former hitting partner for Serena Williams, really just gave her a reality check. He told Osaka to stay calm and wait for her opportunities.
"She's one of the best players in the world. I just have to stay in there, and hopefully I'll get a chance,'" Osaka said. "I did, so I just kept trying to roll with it. He literally told me that."
On-court coaching is allowed at WTA events, but it is banned at Grand Slam tournaments.
The 21-year-old Osaka will play Lesia Tsurenko, a 7-5, 6-3 winner over Anett Kontaveit, in the semifinals. She could rise to No 3 in the rankings next week - which would be a record high for a player from Japan.
Nishikori, who became the highest-ranked male player from Asia when he got to No 4 in the wake of his run to the US Open final in 2014, lost the 2017 Brisbane final to Dimitrov. That is so far a one-off, with Nishikori now extending his career record to 5-1 against the Bulgarian.
He will next play Jeremy Chardy, who beat Japanese qualifier Yasutaka Uchiyama 6-4, 3-6, 7-6 (4) to reach the semifinals.
Jo-Wilfried Tsonga got an easier path to the quarterfinals than expected, avoiding a second-round contest with 17-time Grand Slam champion Rafael Nadal, who withdrew with a thigh muscle strain.
Tsonga then beat Taro Daniel 7-6 (5), 6-3.