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(Reuters) - A shockingly unlucky break cost Rory McIlroy probably two strokes at the final hole on Friday, leaving him five strokes from the halfway lead at the U.S. Masters.

If there was any justice, McIlroy would only be three strokes off the pace at Augusta National after he almost literally knocked down the pin at the par-four 18th.

His approach shot from 140 yards looked perfect, but it was almost too perfect, clattering against the pin and ricocheting all the way off the green, stopping 22 yards away.

What would most likely have been a tap-in birdie, or even a hole-out eagle, instead turned into a bogey, after the Northern Irishman chipped to four feet and then missed the par putt for a one-over 73.

“I thought it was perfect,” he said of his approach shot. “I hit a really good shot, just a bit unfortunate.

“It’s frustrating. It’s tough because you grind all day and you battle hard and then something like that happens at the last … but I’m still in decent position going into the weekend.”

There are plenty who fancy the world number two to secure the Green Jacket on Sunday, and with it the career grand slam, with bookmakers installing him as a 10/1 fifth favorite going into the final two rounds.

“I know I have to get off to a pretty fast start tomorrow,” he said. “A good, solid front nine and I’ll be right there in the tournament.”