World No.1 Serena Williams regained her winning mojo to beat Lucie Safarova 6-3 6-7 (1-7) 7-6 (8-6) in a thrilling Hopman Cup clash on Thursday night.
Williams, who was thrashed by Eugenie Bouchard in straight sets on Tuesday, looked set for a cruisey win after going a set and a break up against world No.15 Safarova.
But the game turned on its head after Safarova reeled off four straight games, only for Williams to regain her composure when it mattered most to win the match in 155 minutes.
The US can secure the tie win over the Czech Republic if John Isner beats Adam Pavlasek in the men's singles rubber.
Williams experienced a mystery tiredness during her opening two singles matches, but the 33-year-old felt good against Safarova.
"Yes it's over. Physically I feel like I can run a 10km," Williams said.
"It feels so much better than I did a couple of days ago. I feel really good now.
"I feel like I'm getting back in the groove. I'm not moving as well as I was last year. But I'm going to try to improve that. I know I can. I'm getting there.
"I needed that win. I was over losing to her in Perth. It feels really good to get through that."
The US need to win the tie 3-0 in order to progress through to Saturday's final.
The Czech Republic will progress if they can win one of the two remaining rubbers.
