From the odds favorite to win the British Open, to missing the cut on his home course?

That’s the potential reality now facing Rory McIlroy after his disastrous opening round on Thursday at Royal Portrush.

The native of Northern Ireland, who set the Royal Portrush course record by shooting a 61 as a 16-year-old, struggled out of the gate Thursday and carded an 8-over-par 79.

McIlroy entered the tournament as the (9/1) +900 favorite to hoist the Claret Jug, but odds now favor him to miss the weekend.

He carries 1/8 (-800) odds of missing the cut, and 9/2 (+920) odds of making it, according to Paddy Power.

It was a disaster from the beginning for the local hero, who hit his first shot out of bounds and saw things go rapidly downhill from there.

He opened with a quadruple-bogey 8 on the first hole, briefly righted himself to make the turn at 3-over, and then at the par-3 16th – living up to its nickname of “Calamity Corner” – four-putted for a double bogey.

Locals Aghast

A lazy attempt at a short par putt scooted past, leaving the crowd aghast and opening the door for more trouble.

McIlroy suffered one final blow, a triple-bogey on the final hole.

It was hardly the debut many expected of the world’s No. 3-ranked golfer for the first British Open in Northern Ireland since 1951, particularly given McIlroy’s past success on the Royal Portrush layout.

But the golf course has been renovated extensively since McIlroy shot 61 there as a teenager, with several holes completely rebuilt to meet British Open specifications.

McIlroy is also on the brink of becoming the latest in a long list of players to wilt under the heavy expectations of playing a major championship on their home course.

Big comebacks have occurred in the British Open before—Paul Lawrie rallied from 10 back to win at Carnoustie in 1999, and George Duncan roared from 13 back after the second round at Royal Cinque Ports in 1920.

But McIlroy – now a remarkable 300/1 (+30000) to win in the golf betting markets – will need a strong second round on Friday just to give himself a chance at making a historic charge over the weekend.