The same couldn't be said for Ayr outhalf Robbie Fergusson who missed his two attempts at goal before centre Ross Curle took over the duties kicking his side's only points after 32 mintues closing the gap to three points, 6-3, which is how it remained going in at the break.
Munster with most of the possession looked the more threatening in attack with the young backline showing their pace and power breaking the Ayr defence, but they were unable to convert the possession into points. Frustratingly any momentum seemed to end in a forward pass or knock-on.
A missed try scoring opportunity came after 36 minutes with Declan Cusack opting to chip ahead, with Ronan O'Mahony and Hanrahan chasing down the line, the Ayr winger scrambled and mis-judged his dive with O'Mahony in pursuit and Hanrahan scooped up the loose ball to only drop it over the line.
The visitors were reduced to 14 men with Ross Curle binned just before the break.
The second half was a similar affair with Munster dominating but no points to show for it only for JJ's 48" penalty which also yielded another yellow for Ayr, prop Moray Low the offender this time.
Paddy Butler carried well coming off the back of the scrums and Duncan Casey made yards each time with ball in hand, and on a further positive Peter Borlase made his return to action in the 59th minute.
Munster's six point lead didn't look so certain when Butler picked up the first of Munster's yellow cards in the 75th minute, and you would be forgiven for thinking that was the last of him. Ayr increased the pressure, and momentum shifted in their favour as they attacked the Munster line, dominating the scrums and taking advantage of the reduced opposition.
Garryowen's James Rael's introduction to B&I Cup rugby was a short affair, replacing Duncan Casey after 74" he picked up the second yellow 8" later. The result of which left Munster without any front row replacements and un-contested scrums were introduced to the relief of the home side.
Paddy made a timely return deep into added time after Munster had defended their line ferociously with 13 men. Ayr opted to move the ball out to the backline before Sean Scanlon made a crunching tackle to stop the visitors final attack, ensuring a home victory for the young Munster side.
Head Coach Ian Costello after the win "We left it down to the wire again and just didn't take our opportunities earlier in the game. But our defence and composure showed in the end this time, we were able to hold out with only 13 men and get the win."
Referee: Rhys Thomas (WRU)
Munster: Sean Scanlon; Luke O'Dea (Corey Hircock 66), Tom Gleeson, JJ Hanrahan, Ronan O'Mahony; Declan Cusack, Duncan Williams; David Kilcoyne, Duncan Casey (James Rael 74), Christy Condon (Peter Borlase 59); Dave Foley (Dave O'Callaghan 64), Ian Nagle; Billy Holland Capt., Tommy O'Donnell, Paddy Butler. Replacements: James Rael, Peter Borlase, Dave O'Callaghan, Brian O'Hara, Cathal Sheridan, Cian Bohane, Corey Hircock.