REUTERS - Germany's Alexander Zverev won a battle of the giants to down unseeded American John Isner 6-4 6-7(5) 6-1 and reach the Italian Open final on Saturday.
Zverev's victory made the tall 20-year-old the youngest ATP Masters 1000 finalist since a 19-year-old Novak Djokovic in Miami in 2007.
The German could meet world number two Djokovic in Sunday's final, with the Serbian playing Austrian Dominic Thiem in the other semi-final.
Zverev had looked like wrapping up the match in straight sets after romping through the opener in under half an hour, but a defiant Isner forced a rethink when he took the second set down to a tiebreak.
The German was 5-0 down in the tiebreak but battled back before Isner took the match to a third set with a forehand winner.
Isner, the first American to reach the semi-finals in Rome since Andy Roddick in 2008, had a chance to break with Zverev leading 3-1 in the final set but the German snuffed out the challenge.
Djokovic will make his second appearance of the day when he takes on Thiem at the Foro Italico after beating Argentina's Juan Martin del Potro 6-1 6-4 in a rain-delayed quarter-final carried over from Friday.
The match between Djokovic and Del Potro had been halted with the score at 6-1 1-2, and the Serbian serving, as rain and lightning lashed Rome's Foro Italico.
The 12 times grand slam champion had wrapped up the first set in 44 minutes, after dropping serve in the opening game but then winning the next six.
He needed only one of two match points to finish off Del Potro in just over an hour and a half and reach his eighth Italian Open semi-final.
Thiem shocked seven-times winner Rafa Nadal on Friday but has lost his previous four encounters with Djokovic.
Reporting by Alan Baldwin; Editing by Ken Ferris and Pritha Sarkar