The manager says the 31-year-old must knuckle down on Wanderers' US tour - and is convinced he will benefit from his first pre-season in three years.
Coyle told the Bolton News: "We've got no doubts about his ability but I want to make sure I've got him in peak physical condition. I don't think we have at this club to this point.
"But I know that with a good pre-season behind him, he will be.
"Pre-season is vital, especially when you see players like Ivan Klasnic who haven't had it for a few years.
"That platform for training gets you through the season.
"You can achieve it, but it's very, very difficult when you are out there on your own. It's much easier to work within a group.
"Last year there was a little bit of upheaval with his club, he was trying to do bits on his own, and Ivan will tell you he's the kind of player who needs to be cajoled.
"There was a problem with finance at first because his club wanted £2million but we've managed to do a good bit of business because we got him in for nothing. But it meant he lost that vital five or six weeks of pre-season when he could have been within the group."