Sixth seed Thomas Bellucci is through to the second round of the BMW Open after Mikhail Youzhny retired from their first-round match on Monday.
Brazilian Bellucci had won his previous three encounters with the experienced Russian before they met on the first day of the clay-court tournament in Munich.
The 2010 BMW Open champion Youzhny was unable to end his losing streak against the world number 35, who won the first set 6-3 and took the opening game of the second before Youzhny was unable to continue.
Bellucci had secured three breaks to take charge against Youzhny, a beaten finalist in the event seven years ago, and was on course to secure a second-round meeting with Ivan Dodig when Youzhny retired.
Wildcard Mischa Zverev was unable to bring cheer for the Munich fans as he crashed out 7-5 7-6 (7-5) to Santiago Giraldo.
Lukas Rosol fought from a set down to beat Denis Istomin 6-7 (2-7) 6-4 7-6 (7-2), while Dodig was a 7-6 (7-3) 6-2 victor over Ernests Gulbis.