A disgruntled murmur echoed around the arena when the world number one moved to the verge of a second break with only 14 minutes of the match having passed before frustration gave way to sympathy for Sinner's ailing opponent Pedro Martinez.
When it became apparent that the Spaniard was struggling with a shoulder injury, his every point, near miss, brave scramble for the ball was cheered, but there was to be no mercy from Sinner.
The top seed bulldozed into the last 16 with a crushing 6-1 6-3 6-1 win that will have served as an ominous warning to his title rivals.
The trainer was called on court twice to work on Martinez's injury but Sinner was ruthless, as he set about completing his third consecutive straight-sets victory at the All England Club.
The 23-year-old has dropped 17 games in his first three matches, to equal a professional era record at Wimbledon, at an average of less than two per set and has yet to lose his serve.
Bidding to become Italy's first Wimbledon champion, he will next face Bulgaria's Grigor Dimitrov.
"Very happy with the win but we all saw that he was struggling with his shoulder. When you don't serve well on this surface it is hard," Sinner said. "Huge respect to him to come out here and compete."
STERNER TESTS
If Sinner, who swatted aside compatriot Luca Nardi and Australia's Aleksandar Vukic in the previous rounds, is to add another Grand Slam title to the two he has won in Melbourne and one in New York, he will face sterner tests than Martinez.
The world number 52, who had matched his best Grand Slam performance by reaching the third round, was two breaks and 5-0 down when the trainer was first called onto court.
He then immediately held to love as the crowd roared and Martinez gave a wry smile.
This was not the beginning of a great comeback, however, as Sinner took the set and broke for a 3-2 lead in the next.
Martinez created four break points in the eighth game, but spurned them all and Sinner broke again to clinch the set.
The trainer's second appearance was far less miraculous for Martinez as Sinner raced into a 5-0 lead in the third set and created two match points for the dreaded bagel.
Martinez roused himself to hold but the reprieve lasted one game as Sinner's 11th ace brought up three more match points and the Italian wrapped up victory when the Spaniard sent another return off target.
The opening week could not have gone much better for Sinner, who by conceding only 17 games in three matches equalled the mark of Jan Kodes in 1972 for the fewest in the professional era at Wimbledon.
"Every time you enter a Grand Slam in the first week it is special, even more so at Wimbledon," he said. "We are trying to keep pushing but this week could not have gone better for me."