Rovers Professional Development Phase Lead Coach admits the visit of Stoke City in the FA Youth Cup at Ewood Park will mean his side go into the game as underdogs.
Stoke come into the competition at this stage, whilst Rovers have beaten Tranmere and Wrexham to set up the tie.
And Barr admits his side will need to give everything to find a route into round four.
"It's going to be a big ask of the lads," Billy told iFollow ahead of the clash.
"We played them with a lesser team last time out in the league and they gave us a good beating. The lads are looking forward to the tie and the game plan will be based on how Stoke want to play."
"We've done our work on Stoke, just as we did for the games against Tranmere and Wrexham. We know what to expect - they play wide and have two big target men up top.
"I thought in the last round we started unbelievably well but conceded and were knocked back. We were dominant against Tranmere in round one and will be aiming to replicate that performance. We know just how hard this game will be for us."
Barr has mentioned before that his players have sometimes frozen when playing at Ewood Park and is hoping that can change on Wednesday night.
"Playing at Ewood does things to us for some reason", he said.
"Come 7pm on the night it doesn't matter what we do or say in the build up, we're hoping the lads on the pitch can get used to playing in that environment.
"The players want to end up playing at Ewood Park on a regular basis, ultimately. There will be some stresses along the way because we have to win and there's a bit of anxiety in the crowd that may go onto the pitch.
"We're underdogs, definitely. The spending power that Stoke possess will give them pressure and hopefully we can come out on top."
Kick off is scheduled for 7.00pm at Ewood Park on Wednesday 13th December.
Admission is £4 for adults and £2 for concessions (65+ and ages 17 and under). Season tickets are not valid for this fixture.