Tyrell Hatton won the Arnold Palmer Invitational at Bay Hill with clutch play amid high stress, closing with seven straight pars for a 2-over 74 and a one-shot victory over Marc Leishman.

The 8-iron out of ankle-deep rough over the water to a front pin on No. 13. Par saves from off the back of the green on the 14th and 15th holes because the greens were so brittle they wouldn’t hold anything. The best of all was his 5-iron to 25 feet on the par-3 17th for another par, a satisfying score on this day.

Bay Hill served up the most demanding test this side of a major, and Hatton kept it together down the stretch Sunday for his first PGA Tour victory, and his fifth worldwide.

Hatton finished at 4-under 284, one of only four players who beat par for the week, the fewest at Bay Hill since 1980. So severe was the course that Matt Fitzpatrick closed with a 69 and was the only player to break 70 on the weekend.

Rory McIlroy, one shot behind going into the final round, had a 76 for his highest closing round since a 76 in the 2013 U.S. Open at Merion. He was done in by a double bogey on the par-5 sixth when his 90-yard bunker shot went over the green and against the rocks framing the lake, and another double bogey on the ninth when his tee shot went out-of-bounds left onto the practice range.

He still tied for fifth, his eighth consecutive top 5 worldwide dating to late September.

Sungjae Im, trying to become the first player since David Duval in 1997 to win his first two PGA Tour titles in consecutive weeks, was there with a chance until he came up shockingly short and into the water on the 13th for a double bogey.

The scoring average Sunday was 75.06, the toughest final round at Bay Hill since 1983. Hatton’s 284 was the highest score to win the Arnold Palmer Invitational since it began in 1979.