When SHINEDOWN and THREE DAYS GRACE hit the road along with P.O.D. for a lengthy North American tour next month, one thing will be missing: THREE DAYS GRACE frontman Adam Gontier, who announced his resignation earlier this month from the band he co-founded 20 years ago. According to The Pulse Of Radio, SHINEDOWN singer Brent Smith was asked by radio station TK101 in Pensacola, Florida if Gontier's departure gave him any second thoughts about the tour. "I wish Adam the best that I possibly can for whatever it is that he needs to do in his own journey in his personal life," he said. "Now, I think that it is extremely ballsy of the band, THREE DAYS GRACE, to not only say that they're gonna continue on with the tour, but that they're not gonna let it put a negative spin on anything."

Gontier resigned from THREE DAYS GRACE in late December, with the news going public earlier this month.

While the band chalked his exit up to a "health issue," Gontier himself said he was "inspired by life, to move on and to continue to evolve on my own terms."

His exit comes while the band's fourth album, "Transit Of Venus", is still going strong on the rock radio charts. The group immediately named MY DARKEST DAYS frontman Matt Walst, brother of THREE DAYS GRACE bassist Brad Walst, as lead singer for the upcoming tour.

The SHINEDOWN/THREE DAYS GRACE tour will kick off on February 1 in Moline, Illinois, with dates booked into March.

Meanwhile, THREE DAYS GRACE has shared more details of how Adam Gontier told the band he was leaving, with the group's explanation raising more questions about Gontier's motivations and the way he ended his relationship with his bandmates of 20 years. The band posted a statement online that said, "It had been our desire to keep an internal band matter just that, internal. However, after public statements by Adam we feel the need to give our fans the facts. Here's the exact timeline of events over the past few weeks."

The band spells out that it received a letter on December 21 from Gontier's lawyer, which stated, "Please be advised effective immediately Adam is terminating his involvement with the band THREE DAYS GRACE. Adam has been wrestling with a health issue, outlined in the attached letter (a doctor's letter dated December 14), which would have precluded him from touring with the band in 2013 and he wants the group to continue moving forward as they see fit while not holding them back."

The post from THREE DAYS GRACE added that Gontier made no mention of any health issues during a brief December tour, and that bassist Brad Walst tried to reach out to Gontier via text to see if his decision was final. Gontier texted back, "My decision is 100 percent. My relationship with THREE DAYS GRACE is over."

The band concluded, "How would you feel if you were in our shoes? Someone you had known for 20 years, whom you had grown up with, gone through ups and downs with, shared dreams with, ends that relationship as if you had known him for a single day with a letter from a lawyer."

Gontier has since said that his exit had nothing to do with his health, but rather his desire to "evolve" on his "own terms."

The singer will participate in a charity show on Thursday (January 17) in New York City as a solo artist.

Pictured below: THREE DAYS GRACE