Top seed Marin Cilic battled past temperamental French opponent Benoit Paire 5-7, 6-3, 6-2 for only his second win of the year at the Rotterdam World Tennis on Tuesday.
Cilic, a 2014 finalist, struggled with an out-of-sorts and injured Paire, whose racquet-smashing antics left him flirting with the wrath of the chair umpire in a match lasting more than two hours.
Cilic lost the opening set as Paire, who later suffered a hamstring problem, saved two of set points.
But Cilic slowly began turning the tables in a first-round match in which the Croat committed 39 unforced errors while Paire had 43 and was able to convert only one of 10 break points.
"It was a tough match but that is what I expected," Cilic said. "He is always tricky and difficult, a talented shotmaker - you never know what is coming.
"After I lost the first set I had to keep my level up. I did that, got a break in the second set and things started to roll to my side.
"It was good to get into the match after being a set down and winning in the end, It's good for the confidence, obviously."
Sixth-seeded Frenchman Jo-Wilfried Tsonga was kept guessing by unheralded Greek Stefanos Tsitsipas before grinding out a 6-4, 7-6 (7/2) first-round win.
The 19-year-old wildcard entry came onto the court as a complete unknown to Tsonga, who played the Dutch final in 2011, losing to Swede Robin Soderling.
Tsonga, returning to the Ahoy stadium for the first time since 2014, led by a set and 5-3 in the second set against the 205th-ranked challenger but was unable to kill off the match.
Instead, the 31-year-old had to take it into a tiebreaker, eventually making it into the second round in 89 minutes with four breaks of serve.
"It was difficult as I did not know him at all," said the number 14. "That is unusual on the tour, never seeing someone before at all.
"I didn't know where to play at the start or what to expect. The entire match went like this. He went for it sometimes, other times he stayed back and was waiting.
"He surprised me during the entire match."
In round two Tsonga faces Sydney champion Gilles Muller after the Luxembourg veteran beat Dutchman Tallon Griekspoor 6-3, 6-2 with 14 aces as the number 317 youngster made his ATP main draw debut.
Holder Martin Klizan of Slovakia began his title defence with a defeat of Fernando Verdasco 6-4, 0-6, 6-1 while last year's semi-finalist Philipp Kohlschreiber took out eighth seed Lucas Pouille of France 7-5, 6-2.
Frenchman Gilles Simon overcame compatriot Nicolas Mahut 3-6, 6-3, 6-4.