Greek tennis superstar Stefanos Tsitsipas showed little sign of rust as he returned from an elbow injury but fell to Argentina's Diego Schwartzman in an epic 6-7(5) 6-3 6-3 tie in the ATP Cup Monday.

Tsitsipas, who had surgery in November and missed Saturday's meeting with Poland's Hubert Hurkacz before playing the doubles rubber, took advantage of Schwartzman's misfiring serve to gain the early advantage at the Ken Rosewell Arena.

He grabbed an early break in the second set but lost his way thereafter as Schwartzman clawed his way back and leveled the contest before fending off a late comeback attempt while up 4-2 in the decider to help Argentina stay unbeaten in Group D.

"I was just trying to think that it was his first match for two months after his elbow injury, so I was thinking just to try and be in the match," Schwartzman said.

"I had the chance and I think I was ready. I'm very happy because playing against Stefanos and being a set-and-a-break down is not easy, but I found a way."

Federico Delbonis overcame Michail Pervolarakis 7-6(5) 6-1 earlier to put the South Americans in control.

Earlier, Spain's Roberto Bautista Agut beat world No. 8 Casper Ruud 6-4 7-6(4) in Group A to eliminate Norway, while Georgia was also knocked out after losing to Poland.

Bautista Agut's victory came after Pablo Carreno Busta dispatched Viktor Durasovic 6-3 6-3 to give Spain a 1-0 lead in the tie. The Spaniards, who won their opener against Chile, face Serbia in their last group match Wednesday.

"I'm really happy. Casper is playing unbelievable tennis. He had unbelievable performances last year," said Bautista Agut, the world No. 19.

"Today I played really well, I made very few unforced errors and played aggressively ... I feel happy, I like playing in Australia."

Spain's doubles pairing of Alejandro Davidovich Fokina and Pedro Martinez ensured a clean sweep with a 6-4 6-1 win over Andreja Petrovic and Lukas Hellum Lilleengen.

Kamil Majchrzak put Poland ahead with a 6-1 6-1 win over Georgia's Aleksandre Bakshi in Group D before Hurkacz rallied to beat Aleksandre Metreveli 6-7(5) 6-3 6-1.

Szymon Walkow and Jan Zielinski then beat Aleksandre Bakshi and Zura Tkemaladze 6-7(2) 6-2 10-6 to complete a 3-0 victory for Poland, who can reach the semifinals if it gets past Argentina on Wednesday.