Rory McIlroy’s hopes of winning his fourth tournament as a professional took a nosedive when was outscored by 10 shots by new leader Rickie Fowler in the Kolon Korea Open.

World No 3 McIlroy, who was in a five-way share of the lead after rounds of 68 and 69, crashed to a two over 73 at a sunny Woo Jeong Hills Country Club to slip 10 strokes behind world No 36 Fowler at the venue two hours from Seoul.

The 22-year old American, who is seeking his maiden professional victory, shot a course record-equalling eight-under-par 63 to lead by four from YE Yang on 13 under entering the final round.

Following a fog delay, McIlroy began brightly with birdies at the sixth and eighth but then dropped six shots in his next eight holes before closing with a pair of birdies.

“I had a good finish, but it was not my best day,” McIlroy said. “I played quite nicely over the first few holes, but the pin positions were very tricky. I was two under through eight holes and I felt pretty good, but I missed a little putt on nine which threw me a little.

“I played 10 and 11 pretty well, but I hit a tee shot on 12 which I have not hit that wide all week. And after I hit my first ball out of bounds, I then hit my second in the rough and as I was taking a practice swing I hit another ball which I didn’t see and at first the rules official said that I had played a wrong ball.

“I had no intention of hitting it, but I got it up and down with the other ball and thought I had made seven, but the rules official then said it was OK and I actually made five. That got into my head a little and I lost it a bit on the back nine and I got on a bit of a bad run, but I then played the final two holes a lot better after two good drives.”

Fowler had eight birdies in an immaculate round and believes he can go on now and close out his first win in the professional ranks.

“I had a good round and I can’t complain with a 63,” Fowler said. “Going into the round I wanted to drive the ball well and make some putts, and I was able to do that and that puts me in a good position. My goals were to drive well and putt well, but my overall game was also good.”

Last season’s PGA Tour Rookie of the Year scorched to the turn in five under before following three more birdies with a chip-in par save at the par three 16th.

“I think I can win,” Fowler added. “I feel good about my game and I’m in a great position, which is right where I wanted to be coming into the week.”

Tied for fourth, McIlroy might gain some hope with the knowledge that Yang overcame a 10-shot deficit last year to claim a second Kolon Korea Open title.

World No 43 Yang shot a four under 67 to get to nine under, two better than compatriot Kim Meen-Whee (66).

McIlroy shares fourth place with Australian Bronson La’Cassie (73) on three under.

Kolon Korea Open, after 54 holes (par 71)

200 - Rickie Fowler (USA) 67-70-63.

204 – YE Yang (KOR) 67-70-67

206 – Kim Meen-Whee (KOR) 69-71-66.

210 - Bronson La’Cassie (AUS) 70-67-73, Rory McIlroy (NIR) 68-69-73.

211 - Noh Seung-yul (KOR) 72-69-70.

212 - Mo Joong-kyung (KOR) 71-66-75.

213 - Lee Kyoung-hoon (KOR) 74-71-68.

214 - David Oh (USA) 70-73-71, John Huh (USA) 69-73-72.

215 - Kim Seung-hyuk (KOR) 72-73-70, Hong Soon-sang (KOR) 68-73-74, Lee Soo-min (am, KOR) 68-73-74.

216 - Han Chang-won (KOR) 75-71-70, Kim Kyung-tae (KOR) 76-71-69, Andre Stolz (AUS) 76-71-69, Kang Kyung-nam (KOR) 75-72-69, Park Sang-hyun (KOR) 73-71-72, Terry Pilkadaris (AUS) 73-71-72.