The end of summer has been a very trying time for par.

These fellows with their limber backs and their Jetsons-inspired equipment have been tormenting the number at every turn, giving it a wedgie from Whistling Straits to Conway Farms.

What we required was a reminder that golf is supposed to be somewhat more difficult than some drunken tailgaters’ game of cornhole.

Friday was just such a notice, with a sodden East Lake giving the chummy little field at the Tour Championship all it could handle. The key to turning an already challenging place into the most honest test these guys have faced in more than a month? Just add water.

A magical thing happens when you get this thick Bermuda rough wet. Think Gremlins, only with grass.

The scoring average in dry Thursday’s opening round: 69.7. The average Friday, after more than an inch-and-a-half of rain overnight and a steady misting during the second round: 71.6.

Defying the trend toward more rational scoring was Jordan Spieth, who channeled his April self and finished with the day’s lowest round, a 4-under 66. And still even he, if you caught him at the right moment Friday, was mumbling so that you’d swear the PGA Tour needed to look into starting a concussion protocol just for him.

The day was a testimony to Spieth’s scrambling skills and that diamond-cutter’s touch for which he is known. He missed nine greens and still suffered not a single bogey.

The average winning score in the three playoff events leading to the Tour Championship was 19 under. That number doesn’t budge even if you go back to the last major of the year (the PGA Championship, won by Jason Day at 20 under).

The idea of your 36-hole leader here, Henrik Stenson, going quite so low got a little muddled Friday. While he ran riot out there Thursday, shooting a 7-under 63, Stenson was doing very well to back that up with a 68 on Friday. And even with that, he grew his lead, from two shots at the opening to three at the midway point.

“Two under par around here is never a bad thing,” he said.

Maybe he wasn’t just trying to protect the members’ feelings earlier this week when he suggested that just barely edging into double-figures under par was going to be pretty profitable at East Lake this week.

And a skinny lead may be easier to protect if the conditions remain difficult (there is a chance for more rain Saturday). “Potentially, it’s easier to hang on to three shots, if you keep on making pars around here,” he said.

If you don’t think a little rain makes that much difference, ask Spieth about the 7-iron at No. 10, when he had 185 yards to the hole, the one he hit 135 yards. “And it wasn’t even a bad lie in the rough,” he said.

Spieth broke out the word diabolical to describe what it was like chipping out of the high wet stuff around the greens here.

“When it’s playing as wet as it is now,” said Paul Casey (in third at 5 under), “it just makes it awkward. You can’t get away with anything.”

Ask the formerly hottest golfer in the world, Jason Day, about the conditions after he posted only his second over-par round (71) in his past 30. He is getting a knack for No. 5, though, the hole where he suffered a triple bogey Thursday. He shaved two strokes off that Friday, missing the fairway by about a foot, but still having to try to slash a 3-wood out of the Bermuda tangle from 195 yards out.

“I’m adding on 20 to 30 yards on to the end of a shot (out of the wet rough),” he said.

Ask Rickie Fowler about his adventure out of the high grass on 13, highlighted when he had to flip his club backward to try to extricate the ball from an impossible lie between bunker and green. The resulting double bogey blunted would could have been a more serious move toward the lead (he finished with a 70 Friday and is eight back of Stenson).

Looking ahead to the weekend, whatever the weather, NBC analyst and two-time major winner Johnny Miller tried to write the most appealing script. “We need two or three of them to go down to the wire where the FedEx Cup is there with three holes to go, all (with a chance to win it) near the lead,” he said.

Saturday’s last pairing is Stenson and Spieth, which for now fits that scenario nicely. And perhaps as an added factor, par will have some value as well.