Marin Cilic had to display his battling qualities to beat Gilles Muller and reach the quarter-finals of the Rotterdam Open on Wednesday.
Second seed Cilic, a finalist in 2014, needed over two hours for a 7-6 (7-2) 7-6 (9-7) victory at the Ahoy Rotterdam.
Neither player could force a break-point opportunity in a tight first set, but Muller had to fend off five in the second to keep Cilic at bay.
Muller then fought off two match points in the second breaker but, after failing with a solitary set point, Cilic saw out the match at the third time of asking to set up a last-eight tie with Philipp Kohlschreiber, who defeated Ivan Dodig 6-4 6-2.
Gael Monfils booked his place in the last eight with a nervy 6-3 5-7 6-2 win against Borna Coric.
After taking the first set, Monfils had the opportunity to close it off in the second at 5-4, but Coric rallied to win the next three games and send the match into a third set.
However, the Frenchman proved too good for his 19-year-old Croatian opponent to advance to the quarter-finals.
In round one, third seed Gilles Simon rallied from a slow start to beat Robin Haase 7-6 (7-5) 6-1.
Frenchman Simon - who was knocked out of the Open Sud de France by Dustin Brown in round two last week - was trailing 4-1 in the first set, but he recovered to win the opener on a tie-break and raced through the second in half an hour.
Eighth seed Viktor Troicki celebrated his 30th birthday by coming from behind to beat Andrey Kuznetsov 4-6 7-6 (7-2) 6-3, while Jeremy Chardy won a marathon encounter with Evgeny Donskoy 6-7 (9-11) 6-4 7-6 (10-8).
Elsewhere, Alexander Zverev defeated Vasek Pospisil 7-5 6-2 and Roberto Bautista-Agut was taken the distance in a 7-6 (7-4) 1-6 6-3 win against Joao Sousa.