Belgian ninth seed David Goffin was given a scare after leading 5-1 in the first set before losing six games in a row and dropping the first set to home hope Marco Cecchinato at the Rome Masters on Tuesday.
The Masters Open finalist got back on track by winning the next two 6-2, 6-2 to advance to the second round.
Canadian teenager Denis Shapovalov battled past Czech veteran Tomas Berdych 1-6, 6-3, 7-6 (7/5), a week after becoming the youngest semi-finalist in Madrid.
The 19-year-old will become the new Canadian number one next week in place of Milos Raonic. “I’m a little bit in shock,” he said. “It’s crazy that it’s come so early.”
After a sloppy start Shapovalov found his feet in the second set breaking for a 3-1 advantage after Berdych hit a forehand into the net.
The world number 29 clinched the set, on his third set point of a seven-minute game at 5-3, when Berdych netted a crosscourt backhand.
Berdych came within two points of victory in the ninth game, and Shapovalov raced to the first four points of the tie-break, holding on despite Berdych coming back dangerously for 5/5.
Bosnia’s Damir Dzumhur took 64 minutes to get past Spain’s Fernando Verdasco to meet seven-time winner Rafael Nadal in the second round.
The rain returned in the evening with the match between Croatian fourth seed Marin Cilic and American Ryan Harrison suspended with the first set tiebreak 6-6 (3/3) after 50 minutes play.
Peter Gojowczyk (GER) bt Lorenzo Sonego (ITA) 6-3, 6-4
Philipp Kohlschreiber (GER) bt Jack Sock (USA x13) 6-4, 6-3
David Goffin (BEL x9) bt Marco Cecchinato (ITA) 5-7, 6-2, 6-2
Ryan Harrison (USA) v Marin Cilic (CRO x4) 6-6 (3/3) match suspended because of rain
Damir Dzumhur (BIH) bt Fernando Verdasco (ESP) 6-3, 6-1
Denis Shapovalov (CAN) bt Tomas Berdych (CZE x15) 1-6, 6-3, 7-6 (7/5)
Nikoloz Basilashvili (GEO) bt Filippo Baldi (ITA) 6-4, 4-6, 6-4
Diego Schwartzman (ARG x14) bt Nicolás Jarry (CHI) 6-4, 6-1
Stefanos Tsitsipas (GRE) bt Borna Coric (CRO) 4-1 retired
Lucas Pouille (FRA x16) bt Andreas Seppi (ITA) 6-2, 3-6, 7-6 (7/3)