McIlroy and Day needed low rounds to have any chance of advancing to the weekend and neither was able to produce anything near what was necessary, missing the projected cut by numerous shots.
When they finished their second rounds on Friday afternoon, McIlroy was 4 shots off the cut line and Day a whopping 9 shots removed.
The top 60 and ties make the 36-hole cut, which was projected at 145, 1 over par.
McIlroy is ranked second in the world and Day is third. Both players liked the course, but put their performance down to a lack of execution.
“I’m a big fan,” McIlroy said. “It’s a big golf course with lots of rough but it lets you play.”
McIlroy put most of his difficulties down to lack of competitive golf. He’s twice been sidelined this year due to a rib injury, and has played just the Players Championship since the Masters.
“I need to get competitive rounds, a card in my hand,” he said. “I was a little anxious starting out yesterday and it caught up to me. I’m just excited to get a few rounds and start playing again.”
McIlroy has a hectic schedule again. He’s playing the Travelers Championship next week, then after a week off, heads to the Irish Open, the Scottish Open and The Open in consecutive weeks. After another week, it’s the WGC-Bridgestone and PGA Championship.
That’s eight of the next 10 weeks after just seven starts in 2017.
Day arrived at Erin Hills a week ago and felt “I put in the best preparation for any major in my career,” he said. But he missed his first cut at a major since the 2012 PGA Championship.
“I put it in the wrong places,’ he said. “I enjoyed the walk, the golf course is beautiful but I just didn’t execute.”
McIlroy followed an opening round 78 with a 71 and is now a combined 43 over par in 18 U.S. Open rounds since winning the tournament at Congressional in 2011.
Day added a 75 to his first-round 79 which included two triple bogeys. His total of 154 equaled his worse two-round total at a major, matching his first two rounds at The Open in 2013.
No. 1 Dustin Johnson was outside of the cut line when his second round began after starting the tournament with a 75.
Since the Official World Golf Ranking began in 1986, there has never been a major championship where Nos. 1, 2, and 3 missed the cut.