A medical emergency involving bassist Tobin Esperance has knocked Papa Roach out of its scheduled appearance at Louder Than Life, the band confirmed Friday (Sept. 19), just hours before they were due onstage in Louisville.

The group framed the decision as guided by doctors rather than choice. “After careful consideration and advice from medical professionals, Papa Roach bassist Tobin Esperance will be unable to perform this weekend due to an unexpected emergency,” the band said in a statement via social media, adding that his health was their “immediate concern” and asking fans to respect his privacy.

“Therefore, we will not be able to perform at this year’s Louder Than Life festival, and wish everyone the best. Right now, Tobin’s health is our immediate concern. We look forward to welcoming him back on stage in November and appreciate the continued support and respect for his privacy during this time.”

No detail on what happened was disclosed.

The cancellation costs the band its planned closing date of a U.S. run — the Sept. 19 Louder Than Life slot was set to be their final American show before crossing the Atlantic. That festival itself is no small affair: more than 200 acts are playing across the four-day event, including My Chemical Romance, Iron Maiden, Tool and Limp Bizkit.

Esperance has been part of Papa Roach’s rhythm section since the band formed in 1993, playing on every studio album and co-writing much of its catalog alongside frontman Jacoby Shaddix. That run has produced four Billboard Mainstream Rock Airplay No. 1s — “Kill the Noise,” “No Apologies,” “Help” and “Born for Greatness” — plus the band’s breakthrough “Last Resort,” which spent time on the Billboard Hot 100 in 2000 and remains one of the era’s defining nu-metal singles.

Assuming Esperance recovers on schedule, the band picks back up Nov. 1 for its Rise of the Roach tour, opening at Glasgow’s OVO Hydro and moving through Dublin, Birmingham, Manchester, London and Cardiff before a run of mainland European dates that wraps Dec. 6 in Lyon.