Sinner, fresh from winning the China Open, broke early in both sets to take control and ease himself comfortably into the third round.
The 49th-ranked Altmaier’s best chance came in the eighth game of the first set, but he failed to convert a breakpoint twice, allowing the Italian to hold with an ace.
The second set provided even less opportunity to seriously bother the 24-year-old Wimbledon champion, but afterwards Sinner said it hadn’t been easy.
“It’s very tough… I had not a lot of time to adjust for here, it’s very different conditions (to Beijing),” said Sinner.
Read: https://tribune.com.pk/story/2568877/changing-a-lot-after-us-open-loss-sinner
Sinner’s path to retaining the title this year has been made easier by the withdrawal of great rival Carlos Alcaraz, who dropped out last-minute to rest.
The Italian’s next match is on Sunday against the Netherlands’ Tallon Griekspoor.
Four-time Shanghai champion Novak Djokovic will take to the court again on Sunday as well, facing Germany’s 150th-ranked Yannick Hanfmann.
World number three Alexander Zverev defied a foot problem to book his place in the third round, beating France’s Valentin Royer 6-4, 6-4.
The German had a blistering start, breaking Royer in the first game and then hitting three aces to easily hold the second.
The play settled as the Frenchman found his feet, but a crucial stumble saw him miss a break point in the eighth game, and Zverev took the set.
Both players missed chances to break in the second, wowing the crowd with multiple tense rallies.
Zverev finally broke in the ninth game then held the last game to win, despite having to take a medical break after limping off court.
“It’s not a nice feeling to finish a match like that,” Zverev said afterwards, wincing.
“I’m happy to be through in two sets and I’ll keep fighting through.”
World number seven Alex de Minaur is through to the next round after comfortably dispatching Argentina’s Camilo Ugo Carabelli 6-4, 6-2.
Russia’s Andrey Rublev, ranked 14th in the world, was upset by qualifier Yoshihito Nishioka 2-6, 6-1, 6-4.
But compatriot Daniil Medvedev dominated qualifier Dalibor Svrcina to advance 6-1, 6-1.