Barnes from Tralee will form a Co Kerry midfield with current U20 international JJ Hanrahan (Castleisland) and there's further pace aplenty in the shape of Sean Scanlon and Luke O'Dea who has scored tries in three of his four Rabo starts to date.
Leinster have their own set of speedsters and perhaps the key to the outcome of this game therefore lies with the respective packs. Munster's preparation included a game against a Development XV in Musgrave Park three weeks ago and perhaps the key to the outcome.
The composition of the back five would appear to give Leinster the edge - captain Rhys Ruddock, Dominic Ryan and Leo Auva'a formed the back row in Leinster's recent Rabo game with Ospreys while Damien Browne was on the bench - but Costello's side have found themselves up against it already this season.
They gave themselves all to do when they lost their opening round game against Llanelli but bounced back to reach the quarter final and record a highly creditable win over Ulster Ravens in Ravenhill but Costello is fully aware of the task that faces his side.
"It's going to be a hugely difficult assignment, we know that. Leinster at home in front of what we're hearing will be a huge crowd, " he said this morning before setting out for the RDS. " But you don't expect anything else at this stage of a competition against opposition like that. But we've a good squad, they've worked hard and I'm confident we'll give a good account of oursleves."
Munster: S Scanlon Cork Con); L O'Dea (Shannon), D Barnes (Dolphin), JJ Hanrahan (UL Bohs), I Dineen (Cork Con); S Deasy (Cork Con), D Williams (Cork Con), D Kilcoyne (UL Bohs), S Henry (UL Bohs), J Ryan (Cork Con), B Hayes (Cork Con), I Nagle (Cork Con); B Holland (Cork Con) capt, B O'Mahony (Clontarf), P Butler (Shannon).Replacements: D Fogarty (Cork Con), P Borlase, P Donnelly (Cork Con), B O'Hara (Cork Con), C Sheridan (UL Bohs), D Cusack (Garryowen), R O'Mahony Garryowen),
Leinster: D Kearney; A Conway, B Macken, C O'Shea, F Carr; N Reid, L McGrath; J McGrath, A Dundon, M Moore; D Browne, M Flanagan; R Ruddock capt, D Ryan, L Auva'a. Replacements: T Sexton, J O'Connell, J Coughlan, J Murphy, M healy, C Marsh, A Boyle.