Kruger had abdominal surgery two weeks ago with a recovery time of six weeks, Chayka said.
"We feel that impacted his play," Chayka said. "We're not making this trade believing that we're acquiring the Marcus Kruger of the Carolina Hurricanes. For whatever reason, it wasn't a fit; it didn't work out for him there. He never got the traction in his role that allowed him to have success. … We think [the surgery] will get the jump back in his game that makes him an effective player."
Kruger said, "I'm still pretty fresh out of surgery but I feel good. We've got a long way to go until training camp, so that shouldn't be bugging me more."
Martinook, a 25-year-old forward, had 15 points (six goals, nine assists) in 81 games with the Coyotes this season. He has 65 points (26 goals, 39 assists) in 247 NHL games during four seasons with Arizona, which selected him in the second round (No. 58) of the 2012 NHL Draft.
"I didn't even know a trade could happen this time of year," Martinook said. "When I got that call, it was very shocking, but I've had an hour or two hours to let it sink in. Carolina is kind of a similar situation to Arizona with a lot of young talent up and coming, so I'm excited to join that and put my stamp on it."
Martinook, who was second to Brad Richardson in shorthanded ice time per game among Coyotes forwards (2:05-1:50), played wearing a cast for a torn ligament in his left thumb.
"I didn't have as good an offensive year as I would have wanted," he said. "I was dealing with a pretty significant injury the second half of the season and that hampered my game a little. ... It was definitely harder to create some offense. I could have got surgery but I chose to play and that was my decision. They said it's healed enough that they're confident it should be good for training camp. Coming in healthy, hopefully I'll have a good start."
NHL.com correspondent Craig Morgan contributed to this report.