The veteran Munster second row will now miss the second and third internationals in Melbourne and Sydney, with Rowntree stating that England's Geoff Parling is in pole position to take over at the Etihad Stadium this Saturday.
"Paul's a massive loss. He's such a big influence on the group. He's playing exceptionally well, but you've got to get on with these things, that's why we brought so many players," said Rowntree.
"Whether he's going to stay or not, I'm not sure yet. I'd like him to because of the influence he has around the group, but we'll find out in the next few days what he's going to do.
"I'm not going to try and lie (about Parling starting on Saturday): Geoff is our next lineout caller as such and he's been doing very well coming off the bench and he's taken his chance when he's started as well. We've got good cover there so it's a chance for him.
"With the Lions you've just got to roll with the punches in terms of injuries and changes of personnel and moving every couple of days. You know that when you accept the challenge of being a coach on a tour like this."
So rather than worry about what might lie ahead, who might be the next to suffer a setback or who would step in should someone drop out, Rowntree and co will just focus on the here and now, confident in the fact that this group of players won't be distracted from the task ahead.
"As I keep saying, you don't get a settled build up on a tour like this. That's what makes it so special. You're coaching every day with different people and different challenges. I've got two sets of lineout calls going around my head at any one time, which is not good! You've just got to get on with it… because you've always got the next challenge around the corner," added Rowntree.
"We're changing things at the last moment, changing venues, changing what we're training and how we're training, but the lads' attitude has been exceptional. It helps working with players with that kind of attitude."