Munster made it to the finish line with fourteen men in the last ten minutes to see off Ospreys 22-16 at Thomond Park on Sunday.
But victory was marred by Paul O'Connell's European comeback lasting barely 10 minutes as he was sent off in an absorbing Pool 3 victory.
Referee Christophe Berdos reached for his red card in the 70th minute after Ireland lock O'Connell, introduced on the hour mark as he continues his return from a long injury lay-off, was seen swinging his right arm into the face of Jonathan Thomas as he held him back.
Munster were leading 22-16 at that stage and a late Alan Quinlan turnover staved off any hopes the Ospreys had of posting a famous win.
The Welsh region came to Limerick with plenty of belief and led for much of the first half, until Ronan O'Gara's last-minute penalty gave Munster an 8-6 advantage.
Tommy Bowe's 42nd-minute interception try had the Ospreys 13-8 in front but while Paul James was in the sin-bin, Munster's David Wallace and Johne Murphy crossed for converted tries.
Dan Biggar closed the gap to six points before the dismissal of replacement O'Connell proved a major talking point.
Following up on a forceful opening scrum from his forwards, Biggar stroked over a second-minute penalty to signal the Ospreys' intent.
The Welshmen continued to impress until poor defending from Richard Fussell, filling on for the injured Shane Williams, allowed Doug Howlett in for his third try in two pool games.
Fussell was then caught far too flat as Tomas O'Leary threaded through a perfectly weighted kick and Howlett raced up to gather and score in the corner.
O'Gara's missed conversion was followed by an immediate response from the Ospreys, with Biggar slotting a second penalty after Damien Varley went off his feet at a ruck.
O'Gara missed a chance to reply from the 10-metre line, but as the battle at the breakdown intensified Munster began to find some rhythm.
Paul Warwick raided into the 22 after quick hands from O'Gara, however the latter was off target with his third shot at the posts - a 45-metre penalty from the right after Marty Holah had infringed.
Holah's back-row colleague Jerry Collins bounced off Keith Earls and set up a penalty on the left for Biggar, whose effort tailed away to the right.
As half-time loomed, the Wales out-half found acres of space with a clever kick to the right and Munster hearts skipped a beat as James Coughlan collected the bouncing ball just inches ahead of the onrushing Tommy Bowe.
Pressure from the Ospreys resulted in a worrying amount of turnovers for Munster, but another break out wide from Warwick preceded O'Gara's first successful kick of the afternoon.
Munster came out firing at the start of the second half, Howlett finding space in midfield and Varley rumbling up to five metres from the try-line.
The Ospreys held out and just when it looked like the hosts would convert an overlap on the left, Bowe gobbled up Sam Tuitupou's loose pass inside the 22 and broke clear to score under the posts. Biggar's simple conversion put five points between the sides.
Coughlan slalomed through the Ospreys defence as Munster's forwards took it up a notch and after O'Gara shunned two kickable penalties, a collapsed five-metre scrum saw Ospreys prop James sin-binned.
Four minutes later, support from Coughlan and Mick O'Driscoll helped Wallace muscle his way over the line from close range. The extras from O'Gara moved Munster back ahead.
With the Ospreys still down to 14 men, a wayward up-and-under from Biggar broke for O'Leary to set up Murphy for a well-taken try, to the left of the posts.
But Munster had a rocky road to the final whistle, a scrum infringement allowing Biggar to boot the Ospreys to a losing bonus point.
The off-the-ball incident involving O'Connell, who is just back from a long-term groin injury, was then followed by a missed 54-metre penalty from Barry Davies, as the sides played out a scrappy finish.
Tries: Howlett, Wallace, Murphy
Con: O'Gara 2
Pens: Biggar 3
Munster: 15 Paul Warwick, 14 Doug Howlett, 13 Keith Earls, 12 Sam Tuitupou, 11 Johne Murphy, 10 Ronan O'Gara, 9 Tomas O'Leary, 8 Denis Leamy (c), 7 David Wallace, 6 James Coughlan, 5 Mick O'Driscoll, 4 Donncha O'Callaghan, 3 Tony Buckley, 2 Damien Varley, 1 Wian du Preez.
Replacements: 16 Mike Sherry, 17 Darragh Hurley, 18 John Hayes, 19 Paul O'Connell, 20 Alan Quinlan, 21 Peter Stringer, 22 Lifiemi Mafi, 23 Denis Hurley.
Ospreys: 15 Barry Davies 14 Tommy Bowe 13 Andrew Bishop 12 James Hook 11 Richard Fussell 10 Dan Biggar 9 Mike Phillips 8 Jonathan Thomas, 7 Marty Holah, 6 Jerry Collins, 5 Alun Wyn Jones (c), 4 Ryan Jones, 3 Adam Jones, 2 Richard Hibbard, 1 Paul James.
Replacements: 16 Mefin Davies, 17 Duncan Jones, 18 Craig Mitchell, 19 Ian Gough, 20 Justin Tipuric, 21 Jamie Nutbrown, 22 Sonny Parker, 23 Nikki Walker.
Referee: David Pearson (England)