England's Robert Rock was two shots clear of the field at the halfway stage of the Scottish Open after shooting a second-round 63 at Gullane on Friday.
Combined with his opening 64, that gave Rock a 36-hole total of 127, 13 under par, which left him two shots in front of compatriot Tyrrell Hatton and Sweden's Jens Dantorp.
England's Eddie Pepperell and 2015 champion Rickie Fowler of the United States were a further stroke back.
Meanwhile, former US Masters champion Trevor Immelman was on eight under par alongside first-round leader Luke List.
Rock, yet to drop a shot, is now well-placed to secure one of the three qualifying spots on offer for next week's British Open which this year takes place at another Scottish course in Carnoustie.
The 41-year-old was planning to attend the British Open -- the only one of golf's four 'majors' played outside the United States -- in his role as a coach but could now find himself doubling up.
"I've started well in a few tournaments recently but it's all about putting four rounds together and that's the challenge," said Rock, whose last European Tour title came in Abu Dhabi in 2012, where he played the final round alongside Tiger Woods and outscored him by two, with Rory McIlroy finishing runner-up.
"Getting into the Open is everything, but you have to focus on this event first and play the course here before that," Rock added.
"I hate missing the Open. I'll be there whatever happens as a coach but it's hard going just as a coach and not playing."
Hatton had been the clubhouse leader, having previously enjoyed success in Scotland by winning back-to-back Dunhill Links Championship titles in 2016 and 2017.
Pepperell finished fourth when the Scottish Open was last staged at Gullane three years ago and needs another top-10 spot this week to be in with a chance of taking one one of the three qualifying places on offer for the British Open.
"I'm actually going to be commentating for BBC Five Live for a couple of days if I don't play," said Pepperell, who won his first European Tour title in Qatar earlier this season.
"Obviously I'd rather be playing but we'll just wait and see."
Scotland's Connor Syme set a new course record of 62 earlier Thursday only to see it broken later in the day by Japan's Hideto Tanihara, whose eagle and seven birdies in his opening 15 holes threatened to help him record the first 59 in European Tour history before he signed for a 61.
But five-time major winner Phil Mickelson missed the cut after finishing one under par, with the American -- who on Thursday apologised for his controversial gesture in deliberately hitting a moving ball on the green at last month's US Open -- saying: "I have some work to do on my game, I didn't play great. Now I'll have a couple of extra days to go over to Carnoustie and try to get it done."
English golf player Tyrrell Hatton (here in a photo from June 2018) added a second-round score of 64 to his opening 65 to put himself on 11-under par -- a total that gave him a one-shot clubhouse lead over compatriot Eddie Pepperell at the Scottish Open