Third seed Medvedev booked his place in the last four with a 6-2 7-6 (9-7) win over Nicolas Jarry on Thursday (AEDT).
Sinner had to fight back from two sets down at Melbourne Park in January to beat Russian Medvedev and capture his first grand slam title.
"It's going to be a tactical match, potentially," the second-seed Sinner told reporters.
"I have to be ready if he starts off in a similar way as in Australia.
"I have to be ready and trying to understand it before. Then maybe he's going to change a couple of things. It's going to be an interesting test for me."
Sinner, a finalist in Miami in 2021 and 2023, produced 16 winners to four unforced errors in a stress-free, 91-minute victory.
The opening set of the first quarter-final played in humid conditions hinged on a Machac service game at 3-3 where the unseeded Czech's forehand missed its target on break point to give Sinner a 4-3 lead.
The Italian wrapped up the set with a love hold when Machac was unable to put a second serve back in play.
In the second set, Machac's forehand sailed long to give Sinner the break and a 2-1 lead. Sinner broke again with a backhand winner for 4-1 and closed out the contest with a serve out wide.
1⃣0⃣3⃣ MPH WINNER🥶— ATP Tour (@atptour) Blink and you'll miss it 💥@MiamiOpen | #MiamiOpen | @janniksin pic.twitter.com/J3EsYB4bjDMarch 27, 2024
"I didn't exactly know what to expect today," Sinner said after his 20th win of the year.
"The first games I was looking a little bit what kind of tactics could work or not ... Today I played good, especially in the important moments of the match."
Defending Miami champion Medvedev will represent another tricky test as the Russian has been in imperious form in the tournament, reaching the semis without dropping a set.
He was pushed hard in the second set of his encounter with Chilean Jarry but came through in the tiebreaker, clinching on his third match point.
Daniil Medvedev takes the applause after his win over Nicolas Jarry. (AP PHOTO)
"The first set I feel like I was playing a good level ... and it was enough to win," Medvedev said.
"Tough rallies and tough points. He served better and it was a matter of a few points on the tiebreak, like it is sometimes in tennis ... Happy that I managed to win.
Sinner has lost only one match this year, falling in the semi-finals of Indian Wells to eventual champion Carlos Alcaraz.
"He's (Sinner) playing better and better. He's confident," Medvedev added.
"Even some matches I watch on TV and he's in a little trouble he manages to find solutions and that's what champions do."
