Sinner was the first to step onto the court and while he struggled under the intense heat of the Miami sun he found a way to come back from being a set down and win. It was not an easy match for Sinner who opened with a break but soon found himself on the back foot struggling with the heat.
Eventually, Khachanvo broke him and won the opening set 6-4. After that, it was a struggle for the Russian who barely got any chance on Sinner's serve. In the 2nd set, he would have two break points with one coming late but he used neither. In the tiebreak, he completely faltered allowing Sinner to win it 7-2.
After winning a set without having a break point Sinner felt a boost in confidence. He started playing better with his serve working better as well. A lot of quick points gave him sufficient rest to attack Khachanov late in the set. He broke him and closed it out 6-4.
Medvedev had a bit of an easier time as he did not have to play three hours like Sinner but still Popyrin put up a good fight, at least in the first. The Australian served very well attacking every shorter ball from Medvedev and it worked.
Medvedev had a break point late in the set but Popyrin saved so we went to a tiebreak. In it, it was the Russian who dominated winning it 7-3. The 2nd set was much better by Medvedev who read Popyrin's serve a lot better. When serving for the match allowed himself to get broken which complicated things for a bit.
Medvedev would squander three consecutive match points in the next game allowing Popyrin to make it 5-5. He would then lose the set in a tie-break and fight in the third decisive set. However, the Russian prevailed in the 3rd to win 7-6, 6-7, 6-4 in 159 minutes.