John Lazar / AP

Phil Mickelson pumps his fist after an eagle. Mickelson won the Northern Trust Open tournament on Sunday.

First, he began hitting 3-wood off the tee to gain some confidence. And when he unloaded a tee shot down the 15th fairway, the comeback was under way.

Two behind with three to play, he hammered a 9-iron at the flag on the par-3 16th and made a 5-foot birdie down the hill. Then he hit his best drive of the day on the par-5 17th, reaching the green with a 3-wood and two-putting from 70 feet, making another tough birdie putt from 6 feet above the hole.

“I knew he was going to pull it off at some time, but he waited until the last couple of holes,” said Couples, playing in the final group for the first time since Mickelson beat him at the 2006 Masters.

Mickelson led by as many as five shots when he opened with an eagle for the third straight day, although it might have been the first sign of a struggle to come. The hole was in the middle toward the back, easy to access, yet Mickelson had to make a 40-foot putt.

The next two holes were more obvious.

He had trouble with the sticky kikuya grass, muffing a chip on the second hole to make bogey, and with his driver, hooking his tee shot on the third so badly that it struck a eucalyptus tree 170 yards off the tee, leading to another bogey.

And yet, no one in the final group took advantage.

Couples opened with an eagle from 3 feet, and his wedge on the third hole checked up 3 feet from the cup. He made birdie, but it was a nervous stroke, and he badly missed a 3-foot par putt on the fourth, a 8-foot birdie on the sixth and a 6-foot birdie on the seventh.

Romero went at every flag, but couldn’t make a putt unless it was for par — or bogey.

Stricker made three birdies in a four-hole stretch around the turn, with a 6-footer at No. 12 giving him the lead for the first time all week. He never had another good look at birdie until the 17th, and that was the one he badly needed to make.