Rafael Nadal could be beaten on clay if THIS controversial tactic was used - Briggs

That is the verdict of Daily Telegraph tennis correspondent Simon Briggs.

Nadal lifted his 11th Monte Carlo Masters title on Sunday with an emphatic straight-sets win over Kei Nishikori.

The Spaniard is in action this week at the Barcelona Open where he is also aiming to clinch his 11th crown.

While the 31-year-old has been seemingly impregnable on clay, Briggs has suggested that adopting an underarm serve would knock him off his stride.

“There was one interesting conversation that popped up on Twitter when Craig O’Shannessy suggested somebody should try an underarm serve," Briggs said. 

“Rafa is standing to receive the serve so far back that if you are behind the court you can’t see him if you are sitting in the stands.

“That is becoming a strategy so he can have enough time to take a full swing at the ball.

“There was a debate about this and Mark Petchey said that this would have been against the spirit of things for tactical reasons.

“I don’t see that at all. It would be a perfect legitimate tactic and would disrupt the way he is playing at the moment.”

Nadal retained his world No 1 ranking after his triumph in Monte Carlo.

He will meet either Andreas Haider-Maurer or Roberto Carnalles Baena in the second round at Barcelona after being handed a bye into the last 32.