World number five Dominic Thiem heads into Friday's Australian Open semi-final against Alexander Zverev knowing he will have to put their friendship aside to continue his charge towards a maiden Grand Slam title.
The 26-year-old Thiem, twice a runner-up to Rafael Nadal at Roland Garros, edged the Spaniard in four tight sets to set up a ninth career meeting with Zverev.
"It's funny because it's the first time in a Grand Slam semi-final that I face a younger guy. We're good friends. I'm happy that he's playing so good. He made his breakthrough at a Grand Slam," Thiem, who will be seeking a seventh win over Zverev, said.
"We have no secrets from each other. We've played so many times, also on special occasions already... It's a nice rivalry. It's great that we add an Australian Open semi-final."
The 22-year-old Zverev had long been tipped to break the Grand Slam hegemony of Novak Djokovic, Nadal and Roger Federer but until this week, he had never reached the last four in a major.
When he lost all three of his matches at the inaugural ATP Cup in the lead-up to the season's opening slam, the omens did not look good for his chances of doing well at the Australian Open.
However, Zverev has looked in ominous form throughout the event, dropping only one set en route to the last four.
The German blasted past Swiss veteran Stan Wawrinka 1-6, 6-3, 6-4, 6-2 in the quarter-finals after a slow start.
"It's going to be a close match. Same if two top-10 players play each other in the semis of a slam," Thiem added.
"The deciding moments are small. I'm looking forward to it. I'll try to regenerate as good as possible and then try to be ready 100% for Friday."
Zverev said he was reaping the rewards of not putting pressure on himself.
"This year I came into the Australian Open with absolutely no expectations because I was playing horrible. At the ATP Cup I was playing bad, and the weeks before," said the German.
"I hope I can still continue to play better in the semis and hopefully maybe in the final. The people that I'm going to play aren't getting worse."
That he can be sure of as waiting in the final will be seven-time Australian Open champion Djokovic.
