Top seed Rafael Nadal made an impressive start to the final pre-French Open event with a 6-1 6-0 win over Bosnia’s Damir Dzumhur in Rome.
The 31-year-old, whose 21-match unbeaten run on clay ended last week, had a first-round bye and will play Denis Shapovalov or Robin Haase next.
Elsewhere, Fabio Fognini was roared to victory by a partisan Italian crowd as he upset sixth seed Dominic Thiem.
Great Britain’s Kyle Edmund plays France’s Lucas Pouille after 18:00 BST.
Former world number one Novak Djokovic – who has sunk to a ranking of 18th after six defeats in his 12 tour matches this year – eased past Georgia’s Nikoloz Basilashvili 6-4 6-2.
However Nadal, who is aiming for an eighth title in the Italian capital, looked in imperious form as he saw off Dzumhur in just 61 minutes.
If the Spaniard justifies his status as favourite by lifting the trophy, he will reclaim the world number one ranking from Roger Federer after slipping to second at the start of this week.
Fognini’s victory was far less straightforward, but the 30-year-old eventually prevailed 6-4 1-6 6-3 against last year’s semi-finalist.
“It was a good match, actually, from both of us,” said Austrian Thiem.
“It was a very intense fight, basically from the beginning to the end. So I’m disappointed that I lost, obviously. But game-wise, I’m not really disappointed.”