Schauffele hit a seven-under-par 63 to repeat his first-round score.

McIlroy is tied for seventh on eight under with Ireland's Seamus Power and Scotland's Martin Laird.

Harris English, Nick Hardy, Cameron Davis, Patrick Cantlay and Kevin Kisner are tied for second on nine under.

The quadruple bogey on the 12th was just the sixth of McIlroy's career.

"Yeah, it's golf sometimes I think," he said. "It sort of came out of the blue.

"I haven't made a big number like that or couple big numbers like that in a long time. When you hit a tee shot like on 12, the second one is pretty difficult, you know, and you're sort of guarding against the left one and I missed it right."

World-number-two McIlroy had shared the lead with JT Poston after they shot opening eight-under 62s in Connecticut.

The Northern Irishman was four under after the opening nine holes on Friday, thanks to birdies on the first, third, sixth, seventh and ninth.

However, after going through the opening day with no bogeys, the Northern Irishman had already bogeyed the fifth hole before that disastrous quadruple-bogey on the 12th that was followed by a double-bogey three holes later.

McIlroy came into this week's event having finished tied fifth at last week's US Open - his third top-10 major placing of the season.

At the other end of the leaderboard, American Morgan Hoffman reached two under to make his first cut since 2019.

Among those to miss the 2-under cutline were Jordan Spieth, who shot a 66 on Friday but missed the cut by one stroke, Sam Burns and Rickie Fowler.