AC/DC Moves On: "He's not the Phil we've known from the past."

AC/DC guitarist Angus Young and bass player Cliff Williams say their band mate Phil Rudd's behavior was raising concerns quite a while before the drummer was arrested on multiple charges in New Zealand last week. Williams tells USA Today that while AC/DC was recording its soon-to-be-released album Rock or Bust, "it was tough" to get Rudd to show up at the studio.

Young adds that Rudd also wouldn't turn up for video and photo shoots to promote the record.

"It put us in a spot where we couldn't move forward," explains Angus. "Does the guy show up? Is he reliable to do his job in good shape? We've always been a solid, reliable unit."

The charges the 60-year-old Rock and Roll Hall of Famer faces include methamphetamine and marijuana possession, and threatening to kill. He also initially faced a murder-for-hire charge that was dropped.

Young tells USA Today, "Phil created his own situation." The guitarist adds, "He's a great drummer, and he's done a lot of stuff for us. But he seems to have let himself go. He's not the Phil we've known from the past."

Angus says that while he suspects Rudd's troubles may stem from a drug problem, he doesn't "know the exact situation." Meanwhile, with the band planning to launch a tour in support of Rock or Bust next year, Phil's status in the group is a question mark.

"I can only say, from our perspective, that the guy needs to sort himself out," Young says.

Rock or Bust will be released on December 2.