Rory McIlroy has reacted angrily to criticism of his play by telling a television commentator to "Shut up".
Enough was enough for the US Open champion after finishing his first-round 70 at the Irish Open with a double-bogey six and then reading on Twitter what former European Tour player Jay Townsend thought. The American described McIlroy's course management as "shocking" and "some of the worst I have ever seen beyond under-10's boys golf competition".
Playing a tournament on home soil for the first time since his runaway eight-shot win in Washington in June, the world number four snapped back: "Shut up ... you're a commentator and a failed golfer, your opinion means nothing!"
And when Townsend, runner-up to Sam Torrance at the 1993 Heineken Open in Spain after the final round was cancelled for snow, responded that he stood by his comments McIlroy then said: "Well I stand by my caddie".
Youngest winner of the US Open since 1933, the 22-year-old has had JP Fitzgerald on his bag since the middle of his first full season as a professional in 2008.
"He's been having a go at JP every now and again since then and this was the first time I've responded - it was the straw that broke the camel's back," McIlroy later told Press Association Sport, adding: "Now I've blocked him on Twitter so I won't be reading anything more."
The Northern Irish star had been four under par and leading by two after 10 holes, but bogeyed the 11th and then went from sand into water on the 439-yard last.
"To be honest my fairway bunker play wouldn't be one of the strongest points of my game," he said.
"It was a tough shot over water with a wedge. I was aiming it right and trying to draw it in and sort of overturned it a bit - and caught it a bit heavy."
As for the three-wood tee shot into the sand, he added: "That was what we had played yesterday. You can hit driver and take the bunkers out of play, but that brings the water on the left into play a little bit. I just cut it a little bit too much. It wasn't that bad a tee shot really."