Former Masters Tournament champion Zach Johnson surged to the top of the leaderboard at The Open Championship after the early front-runners failed to hold their positions.
The American, winner at Augusta National in 2007, picked up five shots in as many holes on the front nine - including an eagle three - to take a two stroke lead as he reached the turn at five under.
That was one better than Rafael Cabrera-Bello and two ahead of his fellow Spaniard Miguel Angel Jiménez, who had been five under to the turn and had held a three shot lead before giving strokes back coming home.
Johnson's namesake and compatriot Dustin had also gone out in a four under 32 only to bogey the 12th and 15th.
In favourable scoring conditions on the hard and fast-running Muirfield links, there were more birdie opportunities than usual and several players took advantage early on.
But it was Zach Johnson, beaten in a five-hole play-off at the John Deere Classic on Sunday by teenager Jordan Spieth, who made the most of it.
After a birdie at the third, an eagle at the fifth was the start of him picking up four shots in three holes as he reached the halfway point in 31.
That took him past Jiménez, heading in the opposite direction to finish with a three-under 68 and Cabrera-Bello, whose birdie at the 575 yard 17th allowed him to set the clubhouse lead on four under.
Prior to that former Open Champion Todd Hamilton had enjoyed something of a renaissance with a round of 69 - the first time he had broken 70 at the tournament since the final round of his 2004 victory at Troon.
Johnson extended his lead further with a 20 foot birdie at the 12th, with another Masters Tournament champion Angel Cabrera making inroads at three under through 11 holes.
That was the same score as 1998 Open winner Mark O'Meara after five holes and also Dustin Johnson, who recovered his position with an eagle at the 17th.
Four-time Major winner Phil Mickelson, who is looking for consecutive victories having triumphed at the Aberdeen Asset Management Scottish Open on Sunday, was two under through 14.
His first attempt did not escape the trap, his second got out but then rolled back in and he knocked the third well past the flag to finish with a six, dropping him to three over.
