Sinner was barely troubled on Thursday, dropping nine points on serve before sealing the win in just 71 minutes to reach the last-four in Miami for the fourth time in his career and extending his record of consecutive sets won at Masters 1000 level to 30.
"I feel like starting the match is very important. When you start by going a break up, it gives you already a slightly good confidence," said the 24-year-old Sinner, who took control from the start.
"At the same time, they might be very aggressive, so I try to stay as compact as possible with my shots.
"Also mentally, there can be some ups and downs on both sides, so I try to stay very calm and take the chances I can get. I think today, that was the key."
The Italian, who is aiming to become the first man since Roger Federer in 2017 to win Indian Wells and Miami in the same season, will next face third seed Alexander Zverev.
The German thumped No.18 seed Francisco Cerundolo 6-1 6-2.
The other semi-final will be between Czech 21st seed Jiri Lehecka and French No.28 seed Arthur Fils, who saved four match points before defeating American Tommy Paul in the quarters.
