It's tempting to think that Jack Johnson was swinging in a hammock, strumming a guitar and staring at a sweating, fruity drink when the call came. But whatever the beach bum rocker was doing, he jumped up and quickly answered when asked to fill in for Mumford & Sons after the band had to drop out of their headlining set on Saturday at the Bonnaroo festival.

"I was on my way to Bonnaroo to sit in on a set with my friends ALO last night when we got the call asking if I could possibly help out and cover for Mumford and Sons," said Johnson in a statement about his last-minute main stage gig. "I heard the news about Ted Dwane and was happy to know that he was on his way to recovery."

Mumford were forced to cancel
 their headlining slot following the hospitalization of bassist Dwane this week to remove a blood clot
 from his brain. Earlier this week they postponed two Texas gigs and made no mention of whether they would still play 'Roo.

Though happy to step up, Johnson said the main stage audible did require a bit of scrambling on his behalf. "I called my band and asked if they were up for it," he said. "Long story short - they are headed this way. I've got a lot of lyrics and chords to relearn by Saturday night. I was here to play the first Bonnaroo and it is a very special festival to my band. We are excited to hit the stage again. Get well Ted!"