Jordan Spieth's resilience is his greatest weapon as he searches for a career Grand Slam at the US PGA Championship, according to Rory McIlroy.
Spieth, 24, will become the youngest man to win all four majors if he is successful at Quail Hollow this week, having claimed The Open last month.
McIlroy, a Masters win away from his own career Grand Slam and a favourite to claim the US PGA, lauded the American's mental toughness.
"Obviously starting at the Travelers [Championship] and holing that bunker shot to win... and then he does what he does at The Open. He pulls himself out of another hole," the Northern Irishman said on Tuesday.
"He has got that knack. I call it resilience. I don't know if there's a better word to describe what it is that he has.
"But he has got this resilience where he gets himself in positions in tournaments where you don't think he can come back from, and he does. It's awfully impressive. It's a mental thing.
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"You can stand and hit the shots that he was hitting for those last five holes at The Open on the range, no problem. But being able to do it under those circumstances, under the pressure, that's what makes him so good, being in those situations.
"Yeah, resilience, mentally tough, strong, whatever you want to call it. That's his biggest asset.
"Being able to forget about a bad shot and move on to the next one, that's his greatest weapon."
Spieth staged a superb recovery to win The Open, adding to the Masters and U.S. Open crowns he claimed in 2015.