Daniil Medvedev fired Russia into the final of the ATP Cup on Saturday with a tense 3-6 6-3 7-5 win over an injury-hampered Alexander Zverev after the German destroyed a racket in frustration over a lost service break.
Russia will meet surprise package Italy in Sunday's final after Matteo Berrettini sealed a 2-0 win against Spain by beating Roberto Bautista Agut 6-3 7-5.
Zverev had treatment on a lower back injury in the second set against Medvedev and slammed his racket into the court after slapping a wild second serve into the tramlines to be broken at 5-5 in the deciding set.
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Medvedev had his own wobbles serving for the match but eventually closed it out for a timely confidence boost before the Australian Open, which starts on Monday.
"We're really happy to get the win," Medvedev told reporters after sealing a 2-0 win for Russia.
"I started to make some big serves in big moments. That was a big key against Sascha (Zverev)."
In a madcap finish, Medvedev double-faulted twice on match point and saved five break points before finally wrapping up proceedings with a fierce forehand down the line that Zverev could only push long.
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"Crazy match, happy to win, even if many things I didn't like," said Medvedev, whose team mate Andrey Rublev enjoyed a 3-6 6-1 6-2 win over Jan-Lennard Struff.
Nursing a sore back, world number two Rafa Nadal sat out of another match for Spain, who reached the final in the inaugural ATP Cup last year.
His team mate Pablo Carreno Busta lost 6-2 1-6 6-4 to Fabio Fognini in the earlier match before Berrettini continued his fine early season form against Bautista Agut.
Italy failed to reach last year's knockout rounds without Berrettini but are a different beast with the world number 10, who upset Austria's Dominic Thiem in his unbeaten run in singles.
"Obviously now the confidence is better, it's higher," said Berrettini.
"But, yeah, I felt we could do a great, great week. We're feeling good. We're feeling good energy."
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