Having been dragged into a five-set battle in his opener and forced to negotiate two tiebreaks in the next, the Italian looked increasingly at home on the grass of Court One and gave Brooksby very few opportunities to disrupt his rhythm.
"I'm very happy about the win, I'm trying to improve every day," said Sinner, who arrived at the All England Club without a competitive match on grass courts after his shock French Open defeat in the second round.
"A small step forwards today, trying to get better. If I want to go far in this tournament, there are a couple of things that we need to work on."
The 24-year-old got down to business with little interest in another energy-sapping encounter on a warm afternoon, grabbing a break for a 4-3 lead after Brooksby sent his forehand long, and then motoring through the opening set in only 37 minutes.
World number 81 Brooksby looked to mix it up and drew Sinner to the net more in the next set, but there would be no payoff as the four-times Grand Slam champion countered it with his superb movement and swiftly doubled his lead in the match.
A blistering backhand winner helped Brooksby break first in the next set but top seed Sinner responded immediately and held his nerve after dropping serve late on for a last 16 meeting with Japanese qualifier Shintaro Mochizuki.
"I've never played him (before). Whoever is in the fourth round of a Grand Slam deserves to be there. So it's going to be a tough match," Sinner said.
"I know that he played against a very tough opponent today, so especially on this surface it's unpredictable. If you have a flat on the wrong day, it's tough to get out, so let's see.
"But, of course, I try to look more on my side of the net, trying to be the best as I can in a couple of days. I'm trying to recover as well, and then we'll see how it goes. But it's always special to be back here."
See all the stats from the match
Wimbledon 2026
Wimbledon is taking place from June 29th to July 12th at the All England Club in south-west London. With 128 players in the draw, it is the third of the four Grand Slams of the tennis season and the only one played on grass.
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