Alexander Zverev crashed out of the Italian Open on Tuesday with a 7-5, 7-5 loss to Italian wildcard Matteo Berrettini in the second round.
"The match that I played was horrendous," said Zverev after the match, which took 1hr 48min on the red clay of the Foro Italico.
Zverev, the 2017 winner and runner-up in Rome last year to Novak Djokovic, has had a terrible start to the clay court season with the French Open starting on May 26.
The 22-year-old German lost his Madrid Open title last week, falling in the quarter-finals of Madrid and Munich to Stefanos Tsitsipas and Cristian Garin respectively.
The German has yet to win a trophy this season and stands 4-6 on clay. Zverev had been seeded fourth in the final clay-court warm-up before Roland Garros, and was playing his first game having received a first-round bye.
Last year, Zverev reached the final in Rome beating Berrettini in their only previous meeting. But the 33rd-ranked Italian has been on form capturing his second ATP title on clay in Budapest last month, and reached the final in Munich.
Zverev started with a break in the second set, but lost this advantage immediately. The 33rd-ranked Italian survived four break points, breaking the German in the twelfth game to close 7-5 to the delight of the home crowd.
Berrettini will play Argentine Diego Schwartzman, who eased past Yoshihito Nishioka 6-1, 6-4 in 73 minutes.
Belgian David Goffin rallied from a set down to beat former French Open champion Stan Wawrinka in three sets and advance to the second round.
The 28-year-old Goffin won through 4-6, 6-0, 6-2 in 1hr 55min against the three-time grand slam winner to set up a meeting with Argentine seventh seed Juan Martin Del Potro for a place in the third round.
Ninth seed Marin Cilic beat Italian wild card Andrea Basso 6-1, 7-5 as Australian Nick Kyrgios needed three sets to get past Russian 12th seed Daniil Medvedev.
"I knew it was going to be tough today because I haven't played much on clay," said Kyrios, who next plays Norwegian qualifier Casper Ruud.
Portgual's Joao Sousa saved four match points in the deciding set to battle past American Frances Tiafoe 6-3, 6-7, 7-6.
Sousa, who also trailed 1/4 in the deciding set tie-break, will play third seed Roger Federer in the second round.
Eight time Rome winner Rafael Nadal will open his tournament against Jeremy Chardy in the second round after the Frenchman beat compatriot Richard Gasquet 6-1, 4-6, 6-3 in a match suspended overnight on Monday.