Stan Wawrinka benefitted from a Benoit Paire collapse, with the Swiss carving out a 7-6(7/4), 6-1 win on Monday at the Rotterdam Open.
After fighting through a 45-minute first set the 33-year-old Wawrinka needed just 26 more minutes to salt away the first-round victory as the moody Paire had unleashed a trademark racquet smash after dropping the opening set.
The frustrated 58th-ranked Frenchman made little effort in the second set, phoning it in with apparent disinterest as Wawrinka took complete charge.
Breaking four times on his way into the second round Wawrinka made a date against either Milos Raonic, who beat him in four tiebreak sets at the Australian Open, or German Philipp Kohlschreiber.
"It's tough to play a friend whose game you know so well," Wawrinka said of Paire, "I didn't start well, but I lifted my level and got better and better.
"I'm happy to win this match.
"It's tough to play Paire but I was able to regain my focus. I fought hard to find my rhythm."
Wawrinka said that his knee is no longer a problem.
"In general I'm training well and moving well. "I had a good level in Melbourne against Raonic over almost four hours.
"The knee is good, I'm happy physically and have confidence in it."
The number 68 Swiss who claimed the title in Europe's major port city in 2015, has been working for more than a year to rehab completely following two knee surgeries in summer, 2017.
Victory over his French opponent leaves him with a 9-3 record in the series.
The field is headed by Asia's top player, Kei Nishikori of Japan, who opens in his tournament debut on Tuesday against Montpellier finalist Pierre-Hugues Herbert of France.
In other first-round results on Monday, Italian veteran Andreas Seppi outlasted Peter Gojowczyk of Germany 7-6(7/3), 3-6, 6-2 while Kazakh Mikhail Kukushkin beat Dutchman Robin Haase, a quarter-finalist here in 2018 who lost to Roger Federer, 6-2, 7-6(7/4).
Federer became the oldest man to return to the number one ranking through that victory one year ago here.