McDowell, Jaidee, Aiken and Grace in final four at Volvo World Match Play

KAVARNA, Bulgaria -- Graeme McDowell reached the semifinals of the Volvo World Match Play Championship after knocking out defending champion Nicolas Colsaerts, whose day include the bizarre moment of taking a penalty drop inside a restroom.

McDowell rallied from an early deficit to win 2 and 1 over his European Ryder Cup teammate on the oceanside Thracian Cliffs course and will next face Branden Grace of South Africa, who beat Chris Wood of England 2 and 1. The other semifinal will pit Thomas Aiken of South Africa against Thailand's Thongchai Jaidee.

Colsaerts had the most memorable moment of the day when his tee shot on the short par-4 10th hole flew into a hazard behind a public restroom in a brick building close to the green. Because of where the ball had crossed the hazard line, tournament officials ruled that the penalty drop must be made within the restroom itself, leading to a comical moment that had Colsaerts, his caddie and rules officials all laughing.

''I ain't hitting it out of the loo,'' Colsaerts joked.

He didn't have to. Since it was considered an immovable obstruction he was then given free relief to play from outside.

He ended up saving par and halving the hole.

''I'm sure now the whole episode at 10 is going to make all the TV news programs, Facebook and all the social media sites with the caption: 'Here's some Belgium guy playing golf in some toilet block in Bulgaria,''' Colsaerts joked. ''It's the first time I've ever hit a ball into a toilet block, and you would have thought as a kid I would have been crazy enough to practice that shot. But I never did.''

McDowell is the highest-ranked player in the event at No. 8 and is looking to become the first Northern Irishman to win the event.

''This is an historic event and it's a trophy that has all the legends of the game appearing on it,'' he said. ''I think back to the golden years around Wentworth [the event’s longtime home in England] and watching all of my heroes winning this great, great tournament. And I would dearly love to add my name to that list, but there is three other guys still left in the event who also feel the same way as I do.''

Colsaerts got back into the match with a birdie on the 13th – where McDowell was going to drop at least one shot – and by winning the 14th with a par. However, he missed a birdie putt from seven feet on the 16th to get back on level terms and then hit two clumsy pitches on the par-3 17th to allow McDowell to close out the win.

"I keep giving guys a look in and you don't want to give them too many chances," said McDowell, who almost squandered a four-hole lead with six to play before beating Bo Van Pelt on the 18th in the last 16 Saturday morning. "I was looking like going 4 up on the 10th and Nicolas then literally makes par from the toilet. It's when the Rules of Golf get a bit funny and wacky and people watching will be wondering what's going on, but what a 4 he made."

McDowell insisted that his energy levels were high despite playing 35 holes on Saturday, but Grace and Aiken both admitted to being slightly fatigued.

"Thirty-six holes a day is definitely starting to take its physical toll," said Aiken, who played both his group matches on Friday as one of the eight unseeded players and needed 19 holes to defeat Ireland's Shane Lowry in the last 16. "I wish I was a little bit fitter, but I think if you can get through the match tomorrow morning you'll be extremely focused for the afternoon."

"I have little aches and pains, a little stiff,” said Grace, who ended Brett Rumford's bid to join Nick Faldo and Seve Ballesteros in winning three European Tour events in a row with a 4 and 3 win in the last 16. "It's been a long day and I can't remember the last time I played 36 holes in a day."

Jaidee played 21 holes in his morning victory over Peter Hanson, but showed no tiredness as he overcame Jamieson with the sort of ruthless form that saw him beat match-play specialist Ian Poulter in the group stage.

“I'm playing very well all week,” he said. “I'm very confident with this format. I'm confident in my golf game this week, we’ve won all the matches, and we look forward to tomorrow.”