One bad shot from Rory McIlroy meant it was advantage Thomas Bjorn midway through their third-round battle at the Dubai Desert Classic.
Joint overnight leaders on 13 under par, Northern Ireland's US Open champion twice nosed one in front over the opening stretch.
But on the short seventh - the hole Martin Kaymer aced on Friday - McIlroy pulled his tee shot into the water.
The 22-year-old did well to limit the damage to a bogey with a 20-foot putt, but Bjorn's 18-footer was for birdie and a one-stroke lead, which would have gone to two if only he had not missed a three-foot chance on the ninth.
Lee Westwood finished his second-round 65 with a hat-trick of birdies and when he set off again with three more in the first four holes he was only one behind.
A mixed bag followed from the world number three, however. He failed to to get up and down from a bunker on the sixth, made a four-foot birdie putt on the next, but then drove into the desert scrub at the eighth and bogeyed again.
Two-putting from the back of the green at the long 10th brought him back alongside McIlroy in second place, while Scot Stephen Gallacher - he had a hole-in-one on the 15th in his opening 69 - and German Marcel Siem were only two behind in joint fourth spot on 12 under.
McIlroy and Bjorn holed from 20 and 18 feet respectively on the seventh, but there was a big difference.
While Bjorn's putt was for birdie McIlroy's was for bogey after he had pulled his tee shot into the water.
They exchanged places at the top, with Westwood two behind along with Kaymer after he could not save his par after driving into the desert scrub down the eighth.
Bjorn two-putted the long 10th for birdie - and that after driving on to the
sand - and saved par from a bunker on the next, but it was not enough to keep him out in front on his own.
Westwood had his sixth birdie of the day with a 10-footer at the 12th and
two-putted the 550-yard next for another.
He and Bjorn were 15 under and two in front of McIlroy, who followed a bogey six on the 10th with a 35-foot birdie putt, Siem and also Scotland's Stephen Gallacher after his birdies at the 10th and 13th.
Westwood missed a six-foot birdie opportunity on the 16th, but nevertheless went into the lead on his own as Bjorn failed to get up and down from the previous green.
The 40-year-old slipped into a tie for second with Siem, who had birdied the same hole, while McIlroy was only two behind in joint fourth with Kaymer, Cabrera-Bello, Gallacher and Swede Joel Sjoholm, round in 66 for the second day running.
