Monfils saved all three break points he faced and broke Tsitsipas' serve three times, including in the final game to send off the world number four in 85 minutes.

The victory for the Frenchman, who was playing in only his 11th match of the year due to injury, marked his first top-10 win since he beat Russia's Medvedev in the third round last year at Indian Wells.

Second seed Medvedev, competing for the first time since losing to Carlos Alcaraz in the Wimbledon semi-finals, dominated proceedings from the baseline during his 6-2, 7-5 win over Italian qualifier Matteo Arnaldi.

Former champion Medvedev, whose sole Grand Slam title came at the 2021 US Open, saved the three break points he faced against Arnaldi and produced 29 winners as he wrapped up the victory in 86 minutes.

In other action, Mackenzie McDonald saved the only two break points he faced for a 6-4, 6-3 win over world number seven Rublev that set up a round of 16 clash with Raonic, who is playing in what may be his final tournament on home soil.

The big-serving Raonic, who was given a wildcard berth into the tournament, backed up his first-round upset of ninth seed Frances Tiafoe with a 6-4, 6-3 win over Japanese qualifier Taro Daniel and has now fired down 52 aces through both matches.

In only his sixth match since returning to the tour in June after missing the better part of two seasons due to a series of injuries, Raonic broke Daniel's serve once in each set en route to sealing the victory.

Eighth-seed American Taylor Fritz, who followed up his Atlanta title with a run to the semi-finals last week in Washington, advanced with a 7-6(7), 3-6, 6-3 win over Frenchman Ugo Humbert.