DiMarco and Craig Stadler each earned $90,000 to share the lead after nine holes in the two-day, skins-type event at Treetops Resort. Fred Couples had $10,000, and defending champ Andy North was shut out.
Mickelson, who won nearly $1 million in the first seven years of this event, withdrew after his meltdown in the U.S. Open at Winged Foot.
'I understand why he's not here,' DiMarco said. 'He's got some things he's got to get through, and he'll be all right. We'll see him at the British (Open).'
Every hole on this nine-hole layout in the northern Lower Peninsula is a par-3. Winning a hole is worth $20,000 providing the player validates by either winning or tying the next hole. If the hole is not won, the money carries over to the following hole. Closest to the pin earns a $10,000 bonus.
DiMarco, still recovering from a skiing accident last winter, established himself quickly on this rolling, wooded course that just happens to be part of a ski resort. He earned $10,000 on the first hole when his tee shot was closet to the pin; the hole was halved with pars.
Stadler was closest to the pin at 7 feet, 9 inches on No. 2 and rolled in the birdie putt to win the hole. His effort to validate was thwarted on No. 3, however, when DiMarco birdied from 5 feet, 7 inches.
That made the fourth worth $60,000. Stadler was closest to the pin, but DiMarco validated with two putts from 26 feet, hiking his earnings to $80,000.
Stadler was closest to the pin again at No. 5, but cost himself a shot at $40,000 by banging the 2-foot-11-inch putt past the hole.
Couples birdied No. 6 from 5 feet, 5 inches and turned that into $60,000 with a two-putt par on the next hole.
'I hit a good shot at No. 6,' Couples said. 'I thought there would be a two at the next hole, but there wasn't. The rest of my round was mediocre, but I had a great time.'
Stadler, who was closest to the pin five times, birdied No. 8 from 16 feet, 8 inches and validated with a birdie from just under 14 feet on the ninth for another $40,000.
'I haven't played in a month,' Stadler said. 'As a rule, I generally play pretty well right after a long layoff like that. But sometimes it doesn't last long.'