U2 drummer Larry Mullen Jr. opened up about the serious neck problems that threatened his ability to perform.

The longtime drummer revealed to Rolling Stone that a congenital fusion in a facet joint, worsened by decades of drumming, left him "in a bad way" following the band's 2019 tour. Doctors even suggested he retire.

By the pandemic, Mullen was in too much pain to play. His condition ultimately prevented him from joining the legendary rock group's Sphere residency after his physical therapist warned he wouldn't make it through rehearsals.

Mullen eventually underwent neck surgery despite the risks. "My desire to play again overwrote that," he told the outlet.

A few months later, he began drumming again but discovered his body no longer worked the same way. After returning to the basics, Mullen was eventually able to resume sessions with his bandmates.

He admitted that he still doesn't know whether he'll be able to handle U2's famously lengthy concerts, but he's prepared to adjust.

"Even if I can't play for two and a half hours, if I can play for an hour, that's enough," he said.

U2's upcoming LP, Carnaval De Luz, drops Nov. 13.