Felix Mantilla pulled off a sensational 7-5 6-2 7-6 (10/8) win over Roger Federer to claim his first Masters Series title.
Federer had won 11 straight matches coming into the final and was the overwhelming favourite to claim his fourth title of the season in Rome.
No unseeded player had won in Rome for 40 years, but Mantilla's defensive consistency flummoxed his opponent who failed to produce his best tennis.
"It's incredible. The biggest win of my career," said Mantilla. "To
beat such a strong player as Roger makes it extra special.
"I've played solid tennis all week and physically I've felt
stronger as the tournament has gone on.
"It was far from easy and had he put some of his chances away it
would have been a lot closer."
Federer had 17 break-point chances in the match, but was only able to take three and this proved crucial.
Many came in the first set when Federer was on top, but Mantilla took the one chance that came his way to steal the set 7-5.
From there Federer's form fell away, and although he opened up a 2-0 lead in the second set Mantilla rattled off eight straight games to take it 6-2 and move ahead in the third.
Federer rallied with a run of four straight games of his own, but surrendered his serve once more to leave the set level.
Federer saved two match points in the resulting tie-break, but hit a forehand long on the third to hand Mantilla victory.
"I had my opportunities and wasn't clinical enough, but he was a
tough opponent and played very well, just as he has done all week,"
"It's a bit disappointing for me as I have been playing
consistently well and felt I had a good chance to win here."