Nathaniel Rateliff’s been around. The Colorado-based singer-songwriter has opened for Willie Nelson, Robert Plant, and other acts that know how to fill an arena. But after more than 20 years in the music business, Rateliff and his band, The Night Sweats, take their turn atop the bill as they headline their concert with opening acts Marcus Mumford and Hermanos Guitérrez in Denver’s Ball Arena – the biggest venue that they’ve ever played as the main act.

“It feels a whole lot different being the headliner than it does opening for someone,” Rateliff told The Denver Post. “It doesn’t matter as much when you’re opening if the set’s poor, because it’s not really your show. It falls heavily on the headliner — and in this case, that’s us.”

The world’s biggest musical stars have played the nearly 20,000-seat arena over the years, and it’s something of a test of Rateliff’s continually growing ability to draw crowds. Selling out the 9,545-seat Red Rocks Amphitheater in Morrison is no small feat, but the December 16 show propels them to another level. Tickets for the Saturday concert have already sold out, but the arena is adding more seats to accomodate concert-goers.

Mumford told the Post that opening for his friend Rateliff and company was an easy decision. “I was doing a theater thing at Newport, so he came and played on that,” Mumford said in a phone interview. “It’s that spirit of collaboration I’ve always loved with him. It’s the same with T-Bone Burnett or Brandi Carlisle… When you get to that level of friendship with someone, it’s like, ‘I’m always down to (collaborate), as long as it’s you.’”