Fabio Fognini fought back from the brink to defeat Joao Sousa 5-7 7-5 6-4 and reach the second round of the Monte Carlo Rolex Masters.
The 26-year-old has won more matches on clay in the last 12 months than Rafael Nadal and was the key player in Italy's recent Davis Cup victory over Great Britain.
No 10 seed Fognini was also a semi-finalist in Monte Carlo last year but looked set for an early exit when he trailed Sousa by a set and 5-2.
The Portuguese player got to within two points of victory but Fognini reeled off five games in a row and then edged a tight decider to advance in Monte Carlo.
Asked on Sky Sports how he had pulled out the victory, Fognini said: "I really don't know.
"It was a difficult match. The first match is always difficult. It's like playing at home for me - I was born really close to Monte Carlo. I survived and I'm through to the second round."
Spanish qualifier Albert Montanes set up a second-round clash with defending champion Novak Djokovic by beating Frenchman Benoit Paire 7-5 4-6 6-2.
Radek Stepanek was a much easier winner, defeating Ivo Karlovic 6-1 6-2, and he will next meet Roger Federer, against whom he has lost 13 of 15 previous matches.
Stepanek's Czech Davis Cup team-mate Lukas Rosol is also through after a 7-5 6-1 win over Evgeny Donskoy, while German Philipp Kohlschreiber defeated Simone Bolelli 6-3 6-4.
Clay-court specialist Tommy Robredo of Spain, seeded 11th, made an impressive start to his campaign as he overcame David Goffin of Belgium 6-4 6-1.
Two more Spaniards advanced to the second round as Pablo Andujar beat Edouard Roger-Vasselin 2-6 7-5 7-6 (7-5), while Albert Ramos defeated Jarkko Nieminen 6-2 7-5.