Denis Shapovalov called for tennis officials to take a stronger stand against disruptive fans after he swore at the crowd for heckling during his three-set win over local hope Lorenzo Sonego at the Italian Open on Monday.

Shapovalov lost his cool, was handed a point penalty and was booed by the fans but overcame all those distractions to beat Italy's Sonego 7-6(5) 3-6 6-3 in his opening match in Rome.

The Canadian was given a point penalty after he climbed over the net to point out to the chair umpire the mark on his rival's side of the court, which is prohibited by the ATP rules.

After Shapovalov complained about the punishment to the supervisor while being jeered by the fans, he screamed "shut the f*** up" at the crowd as he believed he was being taunted by one spectator.

"He was just telling me to get off the court, get out of there, waving me off the court. Trying to obviously get under my skin or whatnot," the Canadian told a news conference.

"I think the umpire just needs to keep an eye on it if a player mentions something.

"The reason why (the heckler) didn't get kicked out was because (the umpire) told me he didn't see what happened. That's very understandable. I feel like he kept an eye on him after that. It didn't bother me after that."

The 23-year-old suggested that tennis should follow the lead of other sports where disruptive fans are evicted from the stands.

"I think in the NBA there's a lot of hecklers and stuff like that. They're pretty strict, the security and everything, that (the fans) don't cross the line. If they do, they're kicked out right away."

The world number 16, however, acknowledged his own behaviour was not acceptable.

"Obviously I think it's a heat-of-the-moment kind of thing. I just need to improve with handling myself about that," Shapovalov said.

"But in terms of going forward, I've played in Rome a lot of times. The fans love me here and I love the fans... Even after the match, there were a lot of people standing, waiting for pictures, stuff like that.

"I do really appreciate the sport and the love I get here. I'm super excited to play another match - not against an Italian," he joked.

Naomi Osaka has withdrawn from this week's event with an Achilles injury.

The four-time grand slam champion sustained the problem at the Madrid Open last week and struggled during a second-round loss to Sara Sorribes Tormo.

Osaka said in a statement: "Unfortunately I’m going to have to withdraw from Rome as the injury which I picked up last week in Madrid hasn’t healed yet. It’s an Achilles injury so I need to be careful, especially in advance of Roland Garros."

Meanwhile, veteran Stan Wawrinka claimed his first victory since last year’s Australian Open over 14th seed Reilly Opelka.

Wawrinka, 37, was off the tour for just over a year following surgery on his foot, making his comeback at the end of March.

Opelka, a semi-finalist in Rome last year, looked to be in control at a set and a break up but Wawrinka battled his way back into the match and turned things around impressively against the giant American to win 3-6 7-5 6-2.

Wawrinka said: "In general I was feeling good on the court. Physically I was feeling great. For sure, when you don’t win a match in more than a year, you start to think always about it more than what you should and not focus on the right things.

"In general I think it was a great match, great battle. I stayed positive. I started to feel much better with my tennis by the end of the second set, and the third set. I’m really happy with this victory."

Dominic Thiem is still searching for his first win since making a comeback from a long-term wrist injury.

The Austrian, a former world number three, slipped to a fourth straight defeat since returning to action, going down 6-4 7-6 (5) against Italian Fabio Fognini.

Meanwhile there was a first win for the new 'little and large’ doubles team of 5ft 7in Diego Schwartzman and 6ft 10in John Isner.

The unlikely pairing won a match tie-break to beat Andres Molteni and Santiago Gonzalez 5-7 6-3 10-1.