HOYLAKE, England — With the nasty weather holding off and Royal Liverpool essentially defenseless, everyone took aim at Rory McIlroy.

The British Open began with an unprecedented two-tee start Saturday, with the R&A hoping to get the third round completed even with the threat of severe thunderstorms.

When McIlroy teed off with a four-stroke lead shortly before lunchtime, there was only a light sprinkle and hardly any wind. Not surprisingly, the world’s best players attacked the softened greens with fearless abandon.

Rickie Fowler birdied four of the first six holes. Shane Lowry shot a 4-under 31 on the front side. Even Tiger Woods, coming off one of his worst Open rounds, birdied his first two holes after starting on the 10th tee.

McIlroy, who built his commanding lead with two straight 6-under 66s, got off to a shaky start. He squandered a booming drive in the middle of the fairway, his next shot catching a deep pot bunker next to the green. He barely got it out of the sand and took bogey.

Dustin Johnson, playing in the final group with the leader and his closest challenger at the start of play, stuck an approach to about 5 feet and rolled in the birdie.

Just like that, McIlroy’s lead was cut in half.

McIlroy bounced back with a birdie at the par-5 fifth, returning his score to 12 under, but Fowler was making a strong charge. The 25-year-old American birdied the first two holes, and then knocked in two more at the fifth and sixth to pull within two shots of the lead.