Defending champion Rory McIlroy crashed out of the BMW PGA Championship on Friday, missing the cut for the third time in four years in the European Tour's flagship event.

McIlroy was seeking his third win in four weeks, having followed his victory in the WGC-Cadillac Match Play with a third consecutive top-10 finish in the Players Championship and a seven-shot triumph at Quail Hollow on Sunday.

However, the world number one slumped to a second round of 78 at Wentworth to finish five over par, 15 shots behind clubhouse leader Francesco Molinari.

The 26-year-old admitted his patience was wearing thin after throwing a club in frustration during an opening 71, a situation which never looked likely to improve on Friday.

Bogeys on the third and sixth were followed by a birdie on the eighth, before the wheels truly came off on the back nine with a bogey on the 10th and a double-bogey on the next, where a wild hook off the tee resulted in an unplayable lie and another hook into the crowd with his second attempt.

An unfortunate spectator hit by the ball was thankfully unhurt and received a handshake from McIlroy by way of an apology, but the resulting six left the four-time Major winner needing a great finish to make the cut.

Further dropped shots on the 13th and 16th were followed by a birdie on the 17th, but a three-putt bogey on the last summed up McIlroy’s day and the only good news was a welcome weekend off before his duties as tournament host in next week’s Irish Open at Royal County Down.

“I’m not going to read too much into it,” McIlroy said after his worst score since also shooting 78 in the second round of the Scottish Open last July, which was one of a string of bad Friday performances ended in style during the following week’s British Open.

“It was inevitable at some point that the run was going to come to a bit of an end. I’m sort of back to my usual at Wentworth. It wasn’t great before I won last year and it hasn’t been great after.

“Any time you’re defending a title you want to come back and give it a valiant effort. This week wasn’t really that. I’m not angry. A little disappointed I’m not going to be here for the weekend, but if there was any weekend to miss, coming off the back of three good weeks in the States . . . I’m probably in need of a little bit of a rest.

“If anything good comes out of this, it’s just that I get a couple of days over the weekend to refresh mentally.”

Shane Lowry will lead the Irish challenge into the weekend after producing a stirring second round which saw him fly up the leaderboard at Wentworth.

Beginning day two on two over, last year’s runner-up carded a five-under-par 67, which included five birdies and no dropped shots.

Italy’s Francesco Molinari was delighted to recover from a poor start to retain top spot.

Molinari saw his two-shot overnight lead wiped out with two bogeys in the first three holes, but played the remaining 15 in five under to add a 69 to his opening 65 and set the target of 10 under par.

Byeong-Hun An will join him

That was two shots ahead of in-form Argentinian Emiliano Grillo, who carded a superb 65. Thailand's Thongchai Jaidee got to eight under later in the day after a 66 that included six birdies and no bogeys. Spanish Open winner James Morrison another shot back after a 66.

Three-time European Tour winner Molinari, who has recorded three consecutive top-10 finishes in this event and was joint second behind Morrison in Barcelona on Sunday, said: “I’m really happy.

“The start is really tricky the first three holes. I think I played them okay. My chipping wasn’t good enough on the first and on the third to save par. I managed to steady the ship and made a few birdies coming in at the end, so a good day.

“Obviously I’m delighted to have gone a little bit further under par from yesterday and just need to keep doing the same. I know how hard I’ve been working the last few months, so it’s nice to see that it’s paying off on the course.”

Grillo holed a bunker shot on the 12th and then hit his approach from 255 yards to a matter of inches on the 18th to set up another eagle.

“I am enjoying the moment and playing well and being in contention is what I need. If I keep knocking someone is going to open the door,” said Grillo, who is looking to win his first European Tour event after finishing 11th, third and sixth in his last three tournaments.

“I’ve been looking for a win since I turned pro and it’s going to come soon. There’s a lot going on when you are in contention and you have to be prepared.

“Playing well definitely pushes the confidence up and it’s nice to be on the leaderboard every week. This is a big week, the flagship event of the European Tour and it would be great to win.”

Damien McGrane dropped a shot on the first hole for the second day running but two birdies in three holes got the Meath golfer to three under for the tournament. It would be his last gain of the day as three bogeys saw him sign for two-over 74 to go back to level for the tournament.

Peter Lawrie also made the weekend action on level par after he failed to build on an opening 69, making  four bogeys and a single birdie  in a three-over 75.  

Graeme McDowell and Darren Clarke both shot one-under-par rounds of 71 and look set to make the weekend right on the cut mark of one over.

Niall Kearney’s debut in the event ended after 36 holes after a two-over 74 left the Royal Dublin golfer on two over. Michael Hoey carded a second-straight 75 to finish on six over.