|BMW Championship, third round (US unless stated)|
|-13 Horschel -10 Palmer -8 Kaymer (Ger), B Watson -7 Fowler -6 Garcia (Spa) Selected others:-4 McIlroy (NI), Scott (Aus) E Rose (Eng) +4 McDowell (NI)|
Rory McIlroy endured a difficult third day to fall out of contention at the BMW Championship in Denver.
The Northern Irishman's worst round of the tournament - a 72 - leaves him on four under and nine shots off the lead, held by American Billy Horschel.
American Ryan Palmer retains second after a 67 took him to 10 under.
German Martin Kaymer propelled himself into the running with a 64 but overnight leader Sergio Garcia (Spain) fell away after a disappointing 72.
|FedEx Cup top five after two of four play-off events|
|1. Chris Kirk (US)||4,154 points|
|2. Rory McIlroy (NI)||3,335|
|3. Hunter Mahan (US)||3,311|
|4. Jimmy Walker (US)||2,823|
|5. Matt Kuchar (US)||2,618|
McIlroy, who is second in the points list, got off to a bad start with a bogey at the third and, despite birdies at the fourth, sixth and seventh, a dire triple-bogie at the 12th severely damaged his standing.
"Glad everybody enjoyed my four-putt today," he tweeted. "Always tomorrow to get a few shots back and get up that leaderboard!"
It was the same for Garcia, whose putting let him down as he bogeyed the seventh, eighth and 14th.
However, there were no such concerns for Horschel, who carded a bogey-free round and capped his day with a superb, long putt on the last to give him his seventh birdie of the day and a commanding lead.
"It's going to be a fun day tomorrow," he said afterwards. "Obviously having a chance to win a golf tournament on the PGA Tour, especially during the FedEx Cup play-offs, can go a long way.
"We'll see what happens. If I can just keep doing what I'm doing and maybe I'll be holding a trophy on Sunday."
Palmer, who needs a high finish to get into the FedEx Cup top 30 and reach next week's Tour Championship in Atlanta, was less consistent with six birdies and three bogeys, while Bubba Watson was in typically-aggressive mood to card a bogey-free 66 and move to eight under and joint third with Kaymer.
American Morgan Hoffmann produced the round of the day with a career-low 62, which included nine birdies, to take him to four-under.
His compatriot Chris Kirk - who holds the overall FedEx Cup lead after two of the four play-off events - dropped two shots to move to one over.
American Keegan Bradley pulled out of the tournament before teeing off his third round on Saturday over a potential rules infraction regarding a drop taken in the opening round.
The 28-year-old, who was 11 strokes off the lead at the halfway stage, had lingering doubts over the legitimacy of a free drop taken in Thursday's round after his third shot at the par-four 18th had embedded in grass just above a bunker.
"I just feel withdrawing is the right thing to do to protect the field in the BMW Championship and the Tour Championship next week," said Bradley, whose withdrawal could cost him a place in next week's event in Atlanta.
Bradley's withdrawal comes after fellow American Phil Mickelson also announced he was pulling out of the tournament at the halfway stage in order to focus on the Ryder Cup, which takes place at Gleneagles in Scotland from 26-28 September.