Rory McIlroy believes his error-strewn first round at the Masters will prove costly as he slipped to seven shots off the pace with a one-over 73 (McIlroy 20/1 – To win Masters).

Coming into the first major of the year, the Northern Irishman was the favourite to complete a grand slam of the majors but he knows he will have to improve, and quickly, if he is to have a chance.

McIlroy’s 73 was his worst opening-round since a 74 in 2010 and the Ryder Cup star admitted he’d made too many mistakes, especially on the greens.

He said: “I can accept mistakes if I’m trying and it’s not a mental error, but six bogeys out there is a little too many and I’m just going to need to tidy that up over the next few days.

“There’s not much wind. I made five birdies, that wasn’t the problem. I just made too many mistakes and I’m making mistakes from pretty simple positions, just off the side of the green, 17 and 18 being prime examples of that.”

While McIlroy was contemplating how to get back to among the leading pack, world number one Justin Rose knows he has it all to do to even make the cut (Rose 100/1 – To win Masters).

The Englishman shot an out-of-character 75 on the opening day and is way off the early pace. Rose still feels he has the chance to get back into it on day two, however.

“You want to make the cut, obviously, so get off to a good start,” said Rose, who shot a 40 on the front nine and didn’t make a birdie until the 15th hole.

“If I can get it back into the red for the tournament tomorrow, then you can build a weekend. I feel I can still get to 11 or 12 under, which you never know.”

Hopes of an English winner could rest on Ian Poulter, who is tied for fourth after a four-under 68.  He’s three clear of the next best Brit, Tommy Fleetwood, who carded a one-under round on Thursday.

Brooks Koepka and fellow American Bryson DeChambeau share the lead after opening rounds of 66.

Odds subject to change.