That was three shots behind Fowler and fellow American Xander Schauffele, the 23-year-old having birdied the fifth to claim a share of the lead on his major championship debut. He had no explanation or theory on why the top three players in the world would not be around for the weekend - the first time since the Official World Golf Ranking debuted in 1986 that the top three in the world missed the cut at a major.
At five over par, McIlroy was four shots outside the projected cut mark, while Scotland's Richie Ramsay was one shot outside after shooting a second consecutive 73.
Both players - ranked No. 2 and No. 3 in the world, respectively - put themselves in poor position with bloated opening-round scores: Day a 7-over 79 and McIlroy a 78.
Meanwhile, Graeme McDowell is also in the midst of his second round and is now one shot clear of Dunne on 3-over but also sitting outside the cut mark.
"If you look at the golf course and even talk to me, Jason or Rory, this course sets up flawless for us", Johnson said.
On a day with scoring more hard, Hadwin found his game to be a little off early in the round but he was able to grind out pars with great putting. "I've got to hopefully keep the confidence going, keep the momentum and see if we can have a good weekend and have a chance on Sunday".
McIlroy dismissed the notion of being rusty before the tournament, but conceded on his way out of Wisconsin that he hasn't played almost enough. His third shot went over the back of the green, and it took him five shots from there, including a chip that rolled back to his feet. Lots of talent, just looking for that one break out moment. "I really haven't been hitting the ball well as of late".
"I just didn't putt very well", Johnson said. "Mistakes got exaggerated a little bit more".
After Thursday's round, McIlroy and his coach Michael Bannon discussed his swing issues.
"I just tried to smooth out the transition today", McIlroy said, "and it definitely worked".
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Johnson blamed a failure to generate anything with his putter for his woes. "I just struggled on the greens". The record for a lowest cut was 1-over 145 at Medinah in 1990.
"It's been the best preparation going into a major", Day told reporters. But while seemingly everyone else gripping a club was scoring in red numbers Friday and Saturday, the world's best players were being treated rudely by the first-time U.S. Open course.
Brooks Koepka started on No. 10 and made four birdies on his front nine to get to 9 under, moving into a tie with Fowler for the top spot. Plus, his usually stellar short game deserted him, as he failed to get up-and-down several times in his two rounds.
"I couldn't have shot any higher", Johnson said. "But then again, you sit there and it's the U.S. Open".
"I've shown what can happen with one bad swing".
With its great length, tall fescue rough and vulnerability to wind, Erin Hills figured to give the United States Golf Association exactly what it wanted this weekend - the ultimate test of golf.
He said the width of the fairways negatively affected his focus off the tee.
And they had even more company.
"Being out of position off the tee does not help".