Dustin Johnson, ranked fourth in the world, withdrew Thursday from the 3M Open citing a back injury after he shot a 78 that included four balls hit into TPC Twin Cities’ ponds and lakes in his front nine alone.

His 7-over-par score included what he called a “tap-in” 9, and it followed consecutive 80s he shot last week at the Memorial Tournament, where he missed the cut.

He hit one ball in the water for a double bogey on TPC Twin Cities’ 17th hole — his eighth hole played — and dunked three more in the lake for that quadruple-bogey 9 at the par-5 18th that wrecked his round.

Johnson talked about his morning round afterward and then withdrew about 30 minutes later.

He hit what he called a “perfect” 6-iron from 199 yards over the lake in an attempt to reach the 18th green in two shots and … kerplunk.

Then he hit two more pretty much like it.

“Never once did I think it was going to go in the water,” Johnson said. “Went in the water and I hit two more shots in the water, then I hit a good one, made a tap-in for a 9. Kind of the same last week: I just struggled with my iron play, and it makes it difficult.”

Happy to be back

Five-time tour winner and Thursday co-leader Nick Watney was the first PGA Tour player who tested positive for COVID-19, at last month’s RBC Heritage at Hilton Head. He tested positive for antibodies, negative for the virus and quarantined in South Carolina for two weeks.

“I haven’t really found the proper way to describe being the first guy,” he said. “I felt like I was being cautious and careful and to end up with it was surprising. And then the isolation was kind of like Groundhog Day. We’re in a pandemic and I’m glad to be on the other side.”

He withdrew after Heritage’s first round and missed the cut at the Workday Charity Open two weeks ago. “It’s really nice to be in here talking about golf and not other things,” he said in an interview tent.

Pardon the interruption

Now 249th in the FedExCup standings with two points earned, Zimbabwe-born and Virginia Tech-educated Brendon de Jonge was headed for his hobby farm’s fields Monday morning when 3M Open Executive Director Hollis Cavner called and offered a late invitation.

“I was like ready to get on the tractor and go mow the fields,” he said.

Instead, he packed his bags, golf clubs, everything but his expectations and left his goats, horses and chickens outside Charlotte, N.C., and traveled north. By Thursday lunchtime, he was battling for the tournament lead. His 5-under 66 left him three shots back. He’s in contention thanks to a short game that included holed putts of 53, 41 and 58 feet on his front nine.

“I was two hands on the wheel all day today,” said de Jonge, 40, who turned pro in 2003 and has $12.3 million in career earnings. “I just managed to get around, to be honest. I didn’t know what to expect. I’ve played some social golf at home, but not a lot. I’m not sharp at all. It was a pleasant surprise.”

Etc.

• That was 61-year-old Tom Lehman with the best round of a Minnesota connection pairing that included youngsters Erik van Rooyen and PGA Tour Champions player Tim Herron. Lehman shot even-par 71, Herron 72 and world 42nd-ranked van Rooyen 74 after he hit two in the water at No. 14 and made a quadruple-bogey 8.

• Two-time Minnesota Amateur champ Tom Hoge shot a 69. Gophers golfer and amateur Angus Flanagan shot a 73, as did former Winona State golfer Troy Merritt.

• World No. 6 Brooks Koepka and his brother, Chase, each shot a 70.

• Batting leadoff in Friday’s first group, two-time tour winner Kyle Stanley shot a 6-under 30 on his first nine and was atop the leaderboard much of the morning on his way to a 5-under 66. He rose at 3:45 a.m. and arrived around 5:50 a.m., an hour before his tee time. “It’s nice to get out front and finish early here and go home, get some rest,” he said.