Jack Draper's last-16 opponent at the Italian Open, Corentin Moutet, was roundly booed at the Rome venue after breaking what has been described as an 'unwritten rule'. The pair were in a tense deciding set, which the Brit came out on top for a 1-6, 6-4, 6-3 victory.

Moutet played the fourth-longest match in Italian Open history on Sunday against Holger Rune and tiredness appeared to be creeping into his game, as he sent an underwarm serve towards Draper. The Frenchman's attempt hit the net and he was booed by spectators at the Super Tennis Arena.

Draper was afforded a chance to break Moutet as a result, but the 26-year-old was able to fight him off and ultimately hold, prompting a huge roar from the player to the crowd as he lifted up his fist in celebration.

Then, in the sixth point of the deciding set, Moutet attempted a second underarm serve. But this time he was successful and caught Draper off guard.

Despite the unorthodox serve getting the better of his opponent, Moutet was still booed once more by the Rome crowd that had already sided with Draper in a nervy affair.

Former world No. 5 Kevin Anderson previously described underarm serves as breaking an "unwritten rule" and he would have tried to perfect them if not for potential backlash.

“It’s funny how there is an unwritten rule or code that deems the underhand serve not sportsmanlike," Anderson told the Beyond The Baseline podcast.

“I’ve played a few guys when they return from extremely far back, I sometimes think if that is something I can perfect it would be something worth bringing out. But I guess it is one those things that is not accepted by the tennis world.”

Tempers had already flared in the second set when Moutet raged at the umpire, claiming that there was a double bounce on Draper's shot.

He asked to see multiple different camera angles and pleaded with the official to overturn his decision to award the point to Draper, but ultimately his request was rejected.

The crowd began to turn on Moutet at this point and his further attempts to spice up the contest with a pair of underarm serves only agitated those in attendance.

Having called a medical timeout to address pain in his thigh, Moutet found himself facing a break point and he threw his racket to the ground in frustration as a result. He received a code violation for the outburst before Draper saw out the win.