NEWTOWN SQUARE, Pa. — Justin Rose did his part on another day of low scoring Saturday in the BMW Championship, running off four straight birdies early for a 6-under 64 and a one-shot lead over Rory McIlroy and Xander Schauffele.

At stake for Rose is moving to No. 1 in the world for the first time in his career.

Still ahead is a final round at soggy Aronimink Golf Club that could take more than one day to complete because of rain in the forecast, along with 13 players within five shots of the lead. The list includes Tiger Woods, who shot 66 and made up no ground on the lead.

“If you shoot 65, you were losing ground,” McIlroy said with only slight exaggeration.

Rose made four straight birdies early on the front nine to quickly erase a two-shot deficit to Schauffele, and he finished the front nine birdie-birdie for a 29. Schauffele stayed with Rose the whole way until he three-putted from the tight collar on the 18th hole for a bogey and a 67.

McIlroy picked himself up quickly from a double bogey on the par-3 eighth hole with a 3-wood onto a green so soft on the par-5 ninth that it barely bounced forward and caught a slope down toward the pin, leaving him a short eagle putt.

Three birdies over the last six holes gave him a 63 and a spot in the final group.

The top 30 in the FedEx Cup after the final round advance to East Lake in Atlanta for the Tour Championship. Bryson DeChambeau already has clinched the No. 1 seed with victories in the opening two playoff events.

The more interesting race is at the bottom.

Jordan Spieth salvaged his round late again for a 66, but he still was just outside the top 30. Keegan Bradley made two tough pars for a 66 and narrowly edged past Spieth for the 30th spot.

For Woods, it was another lost opportunity, even though he remains in the mix.

He opened with two straight birdies and the crowd was on his side, loud as ever. He followed with 11 straight pars, even though he had chances from 15 feet and closer.