The United States need Serena Williams to come to the rescue after her teammate Frances Tiafoe lost his opening Hopman Cup clash to Greece’s Stefanos Tsitsipas.

World No.15 Tsitsipas won 6-3 6-7 (3-7) 6-3 in 135 minutes at RAC Arena on Monday, giving Greece a 1-0 lead.

Williams will need to beat world No.41 Maria Sakkari in the women’s singles rubber to keep the tie alive.

The 23-time grand slam winner lost to her sister Venus Williams in an exhibition match in Abu Dhabi last week, and arrives at the Hopman Cup as a major drawcard.

Tsitsipas was left searching for answers after losing to world No.91 Cameron Norrie in straight sets in his opening match.

But the 20-year-old handled the hot conditions far better on Monday, moving freely throughout the match as the temperature soared past 31 degrees.

“I felt a bit uncomfortable in the first match I played. I couldn’t last long. I felt like I was out of breath,” Tsitsipas said.

“But today I felt really comfortable playing the rallies. My shots felt better. In general I felt much more confident, and more me.

“Frances told me he felt the exact same thing I felt in my first match. I told him it was probably because of jet lag and the heat combined.”

Williams’ appearance in Perth is her first tournament since her US Open meltdown, where she was handed a series of code violations in her loss to Naomi Osaka in the final.

The relaxed setting of the Hopman Cup is the perfect place for Williams to ease her way back into competition mode ahead of the Australian Open.

Williams will also be back in action on Tuesday night when the US take on the Roger Federer-led Switzerland.