Speaking after beating Alexander Zverev 6-2, 6-4, and before Medvedev sealed a final spot by defeating top-ranked Carlos Alcaraz, Sinner said the 2021 US Open champion had become noticeably more aggressive this season.
Medvedev endured a disappointing 2025 campaign in which he failed to go past the second round at the Grand Slams and only lifted one title in Almaty but he has been rejuvenated this year, winning trophies in Brisbane and Dubai.
"He's back to very high level. Very big serve, I feel like. He's returning very well, very deep," Sinner told reporters.
"Everyone's trying to be slightly more aggressive. Sascha (Zverev) tried to be more aggressive. He didn't play his best today, but everyone is trying to push."
Sinner and Medvedev have played 15 times in their career with the Italian edging their head-to-head record 8-7.
They will face off for the first time since the season-ending ATP Finals in 2024, when Sinner won his third straight match against the 30-year-old.
"Daniil has found a good, good balance on court, winning a title in Dubai, coming here, making great results," he added.
"But also the last time we played was quite a while (ago) now. So let's see what's coming."
Through to his maiden final in the Californian desert, Sinner is seeking his first title of the year.
"Of course, the next one will be a very tough test, but I'm extremely happy," he said. "We have improved this week, in this tournament, and that for me was the most important part."