Rory McIlroy played through the pain barrier on his way to a brilliant nine under 63 at the Memorial Tournament on the PGA Tour.
The 25-year-old who won the BMW PGA Championship on Sunday has a three shot lead over England’s Paul Casey and Americans Bubba Watson and Chris Kirk.
McIlroy injured his knee on the seventh hole but admitted his wasn’t sure how it happened.
“Honestly, I don’t know how I hurt my knee,” he said.
“I felt it in taking my second shot on the seventh and my foot may have got stuck in the ground a little bit and tweaked my knee.
“So I am going to get some treatment on it now and have a physio look at it but it was painful right after I hit shots but then I sort of walked it off before hitting my next shot and then it became painful again.
“A little ice and some treatment and hopefully it will be alright for tomorrow.”
The 25-year-old had seven birdies and two eagles in a round that had only one blemish, a double-bogey at the par four 14th.
“I put the knee concern out of my mind and when I was over the golf shots. I just pretended it wasn’t there and tried to play the best shots I could. I knew it was going to be a little sore after I hit a shot, especially if I went after a drive or hit an iron shot into a par five,” he said.
“I played really well from tee-to-green and holed a lot of putts, as well.
“I had two really good ups-and-downs at the last two holes and it could have been even better apart from that double bogey on 14.
“So I am really happy and it’s a really good opening.”