The three-time major champion missed the second half of 2017 after undergoing knee surgery following his first-round exit at Wimbledon.

Wawrinka made his return at the Australian Open in January and lost in the second round, but there were signs of promise as he reached the last four in Sofia earlier this month.

However, last time out the Swiss was beaten by world number 259 Tallon Griekspoor at the Rotterdam Open and he was 6-4 1-1 down on Thursday before calling it a day.

Wawrinka was clearly unable to move around the court as he would like and early in the second set of the last-16 clash he decided enough was enough. Ivashka will play Nicolas Mahut, who came from a set down to defeat Gilles Muller 3-6 6-2 6-4.

Before Wawrinka's retirement, Tomas Berdych was staring down the barrel of an upset when world number 129 Stefano Travaglia took the opening set.

Berdych recovered his poise to take a 5-2 lead in the second but when serving to level he was broken as the Italian put away a thumping forehand to close out a monster rally.

Travaglia could not get over the line in the tie-break, though, and a double-fault followed by an errant forehand gave Berdych a 2-1 lead in the decider, the Czech converting his third match point in game nine to see out a 5-7 7-6 (7-4) 6-3 success.

Meanwhile, Karen Khachanov defeated Mischa Zverev 6-2 6-1 and Filip Krajinovic set up a quarter-final with Lucas Pouille by ousting Gilles Simon 6-3 6-3.