Early on, Clark appeared poised to earn his first tour victory.
He took several cortisone shots for neck pain two weeks ago and had said he might skip the British Open even if he qualified at the Deere because he was worried the pain would flare up on the long flight. On Sunday, he said he would have gone but that became a non-issue late in the day.
Clark made a name for himself when he finished two strokes behind Phil Mickelson at the Masters last year. And the South African made another push for the green jacket this year when he was tied for the lead through 36 holes before tying for 13th.
That prize ultimately went to Zach Johnson, who missed the cut at the Deere.
Green was in good position to earn his first tour victory and become the third Australian in four years to take the Deere Classic, but he could not maintain the lead he built the previous two days.
"I just felt terrible with my swing and managed to recover a little bit at the end, but it was a struggle all day,'' Green said.