Munster fell to a 29-19 defeat to Benetton Treviso at Stadio di Monigo on a night when the visitors had four men sent to the sin-bin.
At one stage in the second-half Munster led the Italians by ten points after Stephen Archer crossed for just his second ever try for the province and Ian Keatley converted.
However, Archer later went on to pick up a yellow card eight minutes from time, joining Duncan Williams and Cathal Sheridan as the players to earn a ten-minute time out.
Two tries from flying winger Ludovico Nitoglia gave Treviso their first win of the season, as they scored a second successive win over Munster at Stadio di Monigo.
It had all started so well for Rob Penney's side, and despite Keatley missing a tricky penalty early on, Munster raced into a 5-0 lead when season debutants Simon Zebo and Keith Earls linked up for Earls to score down the right flank.
Keatley was unable to add the extra points, and five minutes later former Leinster fly-half Matt Berquist got Treviso off the mark with a penalty.
Moments later Ronan was shown a yellow card by referee Leighton Hodges, but worse was to follow when Berquist gave Treviso the lead when he slotted the resultant penalty.
Penney would have been delighted to not see a further impact on the scoreboard with a man disadvantage, and with their openside flanker restored, Munster began to improve.
And after a series of powerful scrums under the posts that produced three penalties, Hodges eventually awarded Munster the penalty try that their scrum domination deserved, which gave them a 12-6 lead after 26 minutes.
But the home side hung in there and four minutes from the break Berquist was on target once again with a penalty awarded after Billy Holland failed to roll away from a ruck.
Munster led 12-9 at half-time and that advantage was increased in the 46th minute when Archer got on the back of a powerful rolling maul and Keatley slotted the tricky conversion to give the tourists a ten-point cushion.
But that was as good as it got for Munster as Nitoglia touched down twice in a 12-minute spell for Treviso, to turn the game on it's head.
Either side of his second try, Berquist slotted penalties to give Treviso a ten-point cushion, and with Williams, Sheridan and Archer also seeing yellow, Munster had little hope of mounting a comeback as their Italian adventure ended on a losing note.
Tries: Ludovico Nitoglia (2)
Cons: Matt Berquist (2)
Pens: Matt Berquist (5)
Tries: Keith Earls, Pen try, Stephen Archer
Cons: Ian Keatley (2)
Munster: Denis Hurley (JJ Hanrahan 67); Keith Earls, Casey Laulala (Ivan Dineen 72), James Downey, Simon Zebo; Ian Keatley, Duncan Williams (Cathal Sheridan 61); Dave Kilcoyne, Mike Sherry (Damien Varley 61), Stephen Archer; Donnacha Ryan, Billy Holland (Donncha O’Callaghan 61), Peter O’Mahony Capt (CJ Stander 56)., Niall Ronan (John Ryan 74), James Coughlan.
Benetton Treviso: Luke McLean; Christian Loamanu, Michele Campagnaro, Alberto Sgarbi, Ludovico Nitoglia (Fabio Semenzato 77); Matt Berquist (Alberto Di Bernardo 72), Edoardo Gori; Michele Rizzo, Enrico Ceccato, Alberto De Marchi (Ignacio Fernandez-Rouyet 72); Antonio Pavanello (captain), Marco Fuser (Dean Budd 60); Simone Favaro (Valerio Bernabò 72), Alessandro Zanni, Manoa Vosawai ( Robert Barbieri 51).
Referee: Leighton Hodges (WRU).