“(Those) are my two mental mistakes where I went away from my game plan, cost me two shots,” Reed said.

“I just need to get back to playing on the game plan. I did it perfectly for 18 holes yesterday.”

Overnight leader Reed had earlier started in blistering form, opening with back-to-back birdies to quickly move to seven under for the tournament.

Two more birdies on the fourth and seventh left him at nine under before a bogey at the par three eighth pegged him back.

Reed steadied the ship with three straight pars followed by a birdie on 13, followed by two more pars.

A missed five-footer on the 16th led to a bogey before a brilliant tee shot on the par three 17th left him inches for the hole for a simple birdie.

But a wayward approach on the 18th found a bunker and Reed’s recovery left him with a 24-footer to save par, which came up short as he dropped to eight under overall.

Reed leads Emiliano Grillo of Argentina and Rickie Fowler by two.

Grillo followed up his opening 67 with a 69, a round that could have looked a lot better had it not been for a bogey on the ninth and a double bogey on the 10th.

Fowler, meanwhile, fired a bogey free two-under-par 69 – with two birdies and 16 pars – putting him at six under for the tournament.

One back was Ryan Moore, who shot a three-under-par 68 comprised of five birdies and two bogeys following his opening 69.

Australia’s world number one Jason Day and Jordan Spieth were in a group of five players tied for fifth on four under.

Day shot a one-under-par 70 while Spieth who was disappointed with an even par 71 on Thursday, shot four birdies and an eagle to get back on track. A double bogey on 10 limited his advance, however.

“It was a little difficult out there but I felt like I ground it out pretty good,” Day said. “I know Patrick is up there, and I’m currently four back. Just got to try to get it under par and slowly chip away at it.”

Scotland’s Martin Laird, who had shared the lead with Reed after the first round, drifted off the pace with a one-over-par 72.

Northern Ireland’s Rory McIlroy will need to produce a major charge over the weekend after a round which had threatened to leave him within striking distance.

McIlroy finished the day at two under, with consecutive bogeys on the 15th and 16th thwarting his charge as he finished with a two-under-par 69.

“It was nice to get to minus four, the wind wasn’t as bad and the course was playing a little easier,” McIlroy said.

“If there was any day to make a good score today was it,” he added. “It’s been a little stop-start. Just when I feel like I’m getting momentum I get stopped in my tracks a bit.”

Meanwhile, PGA champion Jimmy Walker was among the 41 players who missed the three-over cut.