The Lions face the Rebels in their final midweek clash, with the team consisting entirely of those who missed the 23-21 win over Australia in the opening Test on Saturday.
Despite not being selected for that match, Rowntree is adamant that those lining up against the Rebels have a great opportunity to stake their claim for a place when they meet the Wallabies in the second Test.
"Your midweek team's attitude and intensity makes the series - we've said that right from the outset," said Rowntree.
"On Saturday they were the ones straight into the changing room after the game congratulating the lads and they're the guys who had to get up on Sunday morning and train. We were very careful about how we picked the squad with that in mind. Their attitude has been impeccable so far.
"Those guys have all been told they have a chance to make the Test squad. For the squad that takes the field [on Tuesday], there are a lot of opportunities there for guys to be involved at the weekend. I am sure there will be a handful of guys who take the field on Saturday who will play [on Tuesday]."
The match with the Rebels gets underway at 10.40am.