Zach Johnson opens with a 66 at Muirfield

Coming off a playoff defeat last week, Zach Johnson posted a 5-under 66 Thursday morning to grab the early lead at the British Open Championship.

The 2007 Masters champion is the clubhouse leader as the feature groups from the early wave have completed their rounds at Muirfield Golf Club.

Johnson shared ninth place last year at Royal Lytham & St. Annes for his best finish at the Open Championship. The 66 matched Johnson's second-best score, as he also carded a 66 in round three last year after opening with a 65.

Spain's Rafael Cabrera-Bello carded a 4-under 67 for second place. Another Spaniard, Miguel Angel Jimenez, shot 3-under 68 and was joined there by Americans Dustin Johnson and Brandt Snedeker.

Former Open champ Todd Hamilton managed a 2-under 69 as did Phil Mickelson and Angel Cabrera.

Among those that struggled in the early wave were Jason Day (73), defending champion Ernie Els (74), U.S. Open winner Justin Rose (75) and Rory McIlroy (79).

Zach Johnson, who lost to Jordan Spieth in a playoff last week at the John Deere Classic, did most of his scoring in a five-hole burst on the front nine.

The 37-year-old birdied the third to get into red numbers. He poured in an eagle effort at the par-5 fifth to jump to 3-under.

Johnson followed with back-to-back birdies at six and seven to gain a share of the lead at minus-5. He ran off four pars in a row from the eighth before being the first to 6-under with a birdie on the 12th.

At the 14th, Johnson stumbled to a bogey to cut his lead to one. He wrapped up his round with four consecutive pars to hold the lead.

"I've gotten used to it. I haven't taken the John Deere off since I was invited to it," Johnson said in an ESPN interview about his quick adjustment to the time change after his late arrival on Monday.

"I don't know if there is a perfect formula. A lot guys come early and it works for them, I understand that. I haven't tried that yet, and I'm not saying it doesn't work for me. I do like playing the week before a major for the most part."

Jimenez was in control early as he started with birdies on each of the first three holes, with another birdie at the fifth. After a trio of pars, he birdied the ninth to make the turn with the lead at minus-5.

However, Jimenez dropped shots at 12 and 16 to fall two shots off the pace.