McCann revealed that so far this season he has not had many players banging on his office door demanding to play, such has been Rovers' form.
But, after back-to-back league defeats, he believes some of those who have had few opportunities this term will have questions about his selection plans.
And he says the best way to express them is out on the pitch on Tuesday night.
'The team has been doing well and, barring one or two, I haven't had many knocks at the door which shows the start we have made,' McCann said.
'We're quite open as a staff and if we we need to speak to them we call on them any way. We do a lot of individual work, whether it's video analysis or on the pitch.
'But I think the group knows the team has been in really good form.
'I get it, if we lose a game or two then players are going to be asking questions but the way I see it is ask questions tomorrow night when they're on the pitch.'
McCann says while sticking inside the selection rules of the competition, he will make more changes than he did in the opening Checkatrade Trophy game against Newcastle United U21s.
And he is determined to use the occasion to see what his fringe players have to offer.
He said: 'I'm mindful of the fact that I haven't seen a lot of them, the players.
'I've seen some of them coming off the bench butÂ I know what it's like when you're a player.
'You want to start a game and show what you've got. You've got got that build-up to the game
'This is going to be an opportunity for some of them to get minutes under their belt and also to rest a few that have played every game, travelled to Plymouth and Accrington before another game on Saturday.
'The games have come for us really quickly.
'We've also got to be mindful of the rules in the competition, we can't just pick who we want '“Â although the U21Â teams can. It's frustrating that.
'We have to make sure what we doÂ matches with the criteria.'
Tuesday night's game is must-win for Rovers if they have aspirations of advancing in the competition having surprisingly lost 3-1 to the young Newcastle outfit in the opening group game.
While fielding close to a first choice XI failed to produce a strong performance, McCann said that night will have no bearing on his selection for the Grimsby tie.
'The team that we picked on that night was the right team to pick, for certain different reasons,' he said.
'Whether it was us on a good roll, players wanting to go again, wanting to keep good momentum - there's always different scenarios every time.
'The game tomorrow comes when there are players needing game time.
'Some players are struggling a little bit but will be ok for the weekend.
'And it's also the opportunity to impress and getting involved for Rochdale.'