Jannik Sinner began his Cincinnati Open campaign with a hard-fought 6-4 7-5 win over Alex Michelsen, bouncing back from his injury scare at the Canadian Open last week.

Sinner fell to a quarter-final defeat to Andrey Rublev in Montreal last time out, appearing to struggle with a hip issue throughout that loss after missing the Paris Olympics due to a bout of tonsillitis. 

However, the Italian played down any concerns over his fitness ahead of his last-32 match in Cincinnati, where he was pushed all the way by Michelsen but held firm to advance.

Sinner had to save eight break points in one hour and 52 minutes on court, committing as many unforced errors (19) as his American opponent.

However, breaks in the very first game of the opener and the penultimate game of the second set proved decisive for the Australian Open winner, who will now face either Sebastian Baez or Jordan Thompson for a quarter-final place.

Meanwhile, Stefanos Tsitsipas bounced back from his first-round Canadian Open exit at the hands of Kei Nishikori, fighting from a set and a break down to beat Jan-Lennard Struff 4-6 6-4 6-3.

Speaking after his win, Tsitsipas – who will face Jack Draper or Jaume Munar next – said: "I was down a break, and I managed to keep on fighting and get the break back. 

"Suddenly I felt like I was starting to figure out what really worked behind his serve. He made a few double faults, and I took that chance, got myself in the lead, and I think once I started reminding myself of my best qualities as a player, these things really started working."

Data Debrief: Sinner looking to stay perfect

Sinner's victory improved his record on hard courts to 25-2 for the season, and a first quarter-final berth at Cincinnati is now within his sights.

He has reached at least the last eight at all five ATP 1000 Masters tournaments he has played this year, though his only such title came in Miami in March.