The 25-year-old struck 47 winners, including 20 aces, and won 45 of 54 first-service points against Pella on No. 3 Court to set up a second-round clash against Dutch lucky loser Botic Van De Zandschulp.
Berrettini clinched the first break of the match with a backhand pass in the fifth game, then secured the 37-minute opener with his seventh ace. But Pella responded by mixing up his service placement and gained a 3-2 lead in the second set with a volley winner at close quarters.
Once Berrettini struck a backhand past Pella at the net to take the third set, the Italian ran through the 24-minute fourth set for the loss of 10 points.
Berrettini, who also captured the Serbia Open title in Belgrade (d. Karatsev) and reached his first ATP Masters 1000 final at the Mutua Madrid Open (l. to Zverev), is now 27-6 on the 2021 season. He is currently in seventh position in the FedEx ATP Race To Turin for a place at the Nitto ATP Finals, to be held from 14-21 November.
Van De Zandschulp hit 52 winners for his second Grand Slam match win. The 25-year-old beat French qualifier Gregoire Barrere 6-2, 6-7(4), 6-1, 7-6(3) in two hours and 40 minutes.
Berrettini’s compatriot, 26th seed Fabio Fognini, will take on Laslo Djere of Serbia later on Wednesday for a place in the third round. Djere beat Fognini 6-3, 6-7(2), 6-1 in the Gonet Geneva Open second round.