Melbourne: Stefanos Tsitsipas faces Daniil Medvedev on Friday for a place in the Australian Open final, where eight-time winner Novak Djokovic awaits.
Greece's Tsitsipas once riled Medvedev by calling him "boring", but he now considers the in-form Russian "smart".
The pair first met on court at Miami in 2018 and have played six times, with Medvedev leading their series with five wins.
But Tsitsipas, who came back from two sets down to shock 20-time Grand Slam champion Rafael Nadal in the quarter-finals, won their last encounter at the ATP Tour Finals in 2019.
A war of words erupted between Tsitsipas and Medvedev after their 2019 clash in Shanghai, when the Greek lashed out at the Russian's "boring" play, with his big serve and relentless baseline rallies.
Tsitsipas has changed his mind now, with the 25-year-old on a 19-match win streak dating back to November.
"Medvedev is going to be a difficult task. He's in very good shape, playing good tennis, playing accurate, playing simple," said Tsitsipas.
"Might have said in the past that he plays boring, but I don't really think he plays boring.
"He just plays extremely smart and outplays you."
The 22-year-old Tsitsipas was two sets down and seemed to be heading for defeat against Nadal before launching an astonishing comeback to go through 3-6, 2-6, 7-6 (7/4), 6-4, 7-5 in four hours and five minutes.
"Stefanos is an amazing player, big serve, great volley," said Medvedev, who beat fellow Russian Andrey Rublev over three sets in his quarter-final.
"Tough to play. I think he's improving physically because maybe two years ago could say, yeah, out of five sets it's maybe not bad to play him. I don't think it's the case right now."
Both men head into the semi-final bidding for a maiden Grand Slam title.
Tsitsipas has never gone beyond a semi-final before, falling to Nadal in the last four at the 2019 Australian Open and to Djokovic at Roland Garros last year.
He has his sights set on becoming the youngest Grand Slam champion since Djokovic won the title at Melbourne Park in 2008 and the first Greek, man or woman, to lift a major trophy.
Medvedev will be playing his first semi in Melbourne as he continues to knock on the door of Grand Slam success, having reached the 2019 US Open final, where he was pipped in five sets by Nadal, and the last four in New York in 2020.
Earlier on Rod Laver Arena on Friday the Czech third seeds Barbora Krejcikova and Katerina Siniakova will face Elise Mertens of Belgium and Aryna Sabalenka of Belarus, the second seeds, in the women's doubles final.
With inputs from AFP.