Austrian Bernd Wiesberger, twice a winner this season, took over at the top with a near-flawless second-round 65 in the Portugal Masters.
It looked like being Padraig Harrington's morning at Oceanico Victoria on Friday when he went two clear with six birdies in his first 11 holes.
But in a real mixed bag of a finish the 41-year-old Irish star, without a European Tour victory for over four years, had a double bogey, two more birdies and two bogeys, both of those coming when he three-putted.
Harrington's 67 for six under allowed 27-year-old Wiesberger to edge one ahead after five birdies and an eagle two at the 315-yard 15th, his sixth.
The Vienna golfer's lone dropped shot came at the difficult seventh, where his drive picked up mud and his approach finished in the greenside bunker.
Scot Stephen Gallacher and England's Ross Fisher, the joint overnight pacesetters, were among the later starters.
Gallacher resumed with a par to be alongside Harrington in second place, but Fisher bogeyed the first and slipped into a tie for fourth with 48-year-old Spaniard Miguel Angel Jimenez, Swede Fredrik Andersson Hed and South African Jbe Kruger.
Ryder Cup pair Martin Kaymer and Francesco Molinari, playing with their Chicago captain Jose Maria Olazabal, were others off late in the day.
They teed off again at two under, level par and four over, respectively.
