LAKE FOREST, Ill. — A weird vibe will be drifting across Conway Farms Golf Club on Sunday for the final round of the BMW Championship, the third leg of the FedExCup Playoffs.

All but one of the players on the front page of the leaderboard will be thinking as much about playing for second place as they will be about winning.

That’s because catching the runaway Australian train that is Jason Day is going to be extremely difficult.

“You kind of have to look at Jason as far as he’s an outlier, don’t have to worry about him, there’s another tournament going on, and he’s in control of whatever he’s doing,” said Rickie Fowler, who is in a tie for fifth after rounds of 69-66-66 but trails by eight shots. He played with Day the first two rounds.

“There were times where I did get a little bit frustrated as far as like I wanted to hole out a shot or I wanted to finally make a putt,” said Fowler, who watched Day fire 61-63. “You just had to stay as patient as possible.”

Day shot 2-under-par 69 in the third round — his worst score this week by six shots — and yet he increased his lead from five shots after 36 holes to six after 54.

He said he was “out of sorts” a bit in the third round because of the swirling winds, drove his tee shot out of the bounds on No. 13 and still shot 69, which he said felt like an 80 considering his first two rounds.

“To be able to squeak out with a 69 and really feel like I got everything that I possibly could out of today’s round, I think that was the best score I could have shot,” Day said. “Obviously the first two rounds were great, and I think this was one of the more important rounds to get through today, and I’m glad it’s over and I extended the lead by one more shot. Overall I’m pretty happy with how things are going.”

Added to his opening rounds of 61-63 — the 124 total tying the PGA Tour record for lowest total after the first rounds of a tournament — Day is 20 under and leads Scott Piercy (67-65-67) and Daniel Berger (65-64-70) by six shots.

“If he happens to come back, then we may have a chance, but other than that, we’ll see if we can take care of the rest of the group of guys and let Jason do what he does,” Fowler said.

There have been larger collapses in PGA Tour history, so a Day victory is not a lock. But the 27-year-old is trying to win his fifth Tour title of the season and his fourth in six starts. He is playing on a course that is on the short side, is on the saturated side after heavy overnight rains, and is on the birdie side (14 players are double-digits under par).

World No. 1 Rory McIlroy, who will lose his top ranking to Day if the Australian polishes off the victory, has signed for rounds of 68-65-67 and is seven back.

“You want to be out there trying to win the golf tournament, not thinking about trying to finish third or second or whatever,” McIlroy said. “But the tournament is in Jason’s hands right now, and it’s up to us that are behind him to try and get off to fast starts tomorrow, and he needs to come back to the field a little bit.”

Dustin Johnson, who is at 12 under and in a tie for fifth, won’t be thinking about Day when he heads to the first tee for the final round. Instead he’ll be thinking about next week’s Tour Championship by Coca-Cola.

“At this point I’m just trying to put myself in the best situation for next week, and you know, get some confidence with the game, which I’m starting to get a lot more confidence in the putter,” he said. “I feel like I can make some putts. Tomorrow I need to go out and shoot a good number and just try and improve my position in the FedExCup.”

PHOTOS: BMW Championship