Juan Martin del Potro picked up his biggest win of 2017 to date, beating world number 11 Grigor Dimitrov in the first round of the Internazionali BNL d'Italia.
The Argentine, playing just his second clay-court match of the year, was in action for the first time since the death of his grandfather prompted his withdrawal from Estoril.
Having skipped the Australian Open in order to maintain his fitness through the year, Del Potro looked keen to make up for lost time with a fine display against Dimitrov.
The former US Open champion extended his perfect record over the Bulgarian 10th seed to 5-0 with a 3-6 6-2 6-3 success.
Dimitrov has now lost his first game at four events since taking the title in Sofia, and his current malaise was surmised by seven double faults. Kyle Edmund is next up for the Olympic silver-medallist in a battle of big forehands.
WIN 599 FOR BERDYCH
Tomas Berdych (12) was a semi-finalist in Rome four years ago and began his tournament with a 7-6 (9-7) 6-4 win over Mischa Zverev.
A second-round meeting with Carlos Berlocq (d. Robin Haase 6-3 7-5) could provide the Czech with a milestone moment, as victory would be his 600th on the ATP Tour.
Both men have won one of their two previous meetings, with Berlocq having recovered from a first-set bagel to win 0-6 7-5 6-1 in the last meeting three years ago.
Ninth seed David Goffin recovered from a set and a break down to beat Thomaz Bellucci in two and a half hours. The Belgian made the quarter-finals in Madrid and the last four in Monte Carlo, and will hope he does not encounter Rafael Nadal, who dumped him out en route to the title both times.
A left-handed Spaniard does lie in wait in round two, but it is Fernando Verdasco, rather than the 'King of Clay'.
POOR POUILLE PUNISHED
Lucas Pouille appeared to be picking up steam when he reached the Monte Carlo semi-finals and won in Hungary, but he followed up a first-round defeat in Madrid with another opening-hurdle stumble to Sam Querrey.
A semi-finalist in Rome a year ago, Pouille was no match for the big-serving Querrey, who blasted 14 aces on his way to a 7-6 (8-6) 7-6 (10-8) success.
Querrey entered the clay season boasting a win over Nadal on the hard courts of Acapulco, and he remains on course to meet the Spaniard again later in the tournament after this win.
BIG BOYS OUT TO PLAY
Andy Murray (1) and Novak Djokovic (2) are in action in Tuesday's games.
The world number one will take on Italy's Fabio Fognini - a 6-1 6-3 victor over wildcard compatriot Matteo Berrettini - while four-time champion here Djokovic takes on Aljaz Bedene, who was 3-0 up in a deciding set before Gianluca Mager withdrew on Monday.