Defending champion Leonardo Mayer saved a match point before beating Slovakian qualifier Jozef Kovalik 6-7 (8-6) 6-4 7-6 (9-7) to reach his third German Tennis Championships final in five years on Saturday.
Mayer survived an early onslaught from Kovalik in a near three-hour thriller, firing 42 winners, including 28 off his forehand.
Kovalik, ranked 113 in the world, snatched the opening set in a tiebreak but Mayer responded with an immediate early break to force a decider.
Both players struggled to test their opponent's serve in the third set, and it was Kovalik who looked likely to move into the final after grabbing a match point at 6-5 in the final tiebreak.
Mayer, whose two tour-level titles have come on Hamburg clay, fought back with deep return to force an error from Kovalik. Five points later, the 31-year-old Argentine put away a crisp volley to seal a remarkable win.
Standing between him and a third Hamburg title is Georgian Nikoloz Basilashvili, who overcame big-hitting Chilean Nicolas Jarry 7-5 0-6 6-1 in the other semi-final.
