Leinster advanced to the Heineken Cup quarter-finals as Pool One winners after seeing off 14-man Ospreys with a bonus point 36-3 win at the RDS.
Wales lock Ian Evans was sent-off for reckless use of the boot in the 20th minute when the scores were tied at 3-3 - a moment of madness that leaves his Six Nations involvement in real doubt - and the Ospreys also had to cope with first half injuries to Ben John and Ryan Jones.
Two penalty tries and scores from Cian Healy, Jordi Murphy and Isaac Boss, with fly-half Jimmy Gopperth kicking11 points, saw Leinster progress, as Dan Biggar's early penalty remained Ospreys' only score.
Gopperth and Biggar swapped penalties in the first 13 minutes, the visitors keeping edgy Leinster at bay until a penalty try and Healy's score shortly before half-time.
It was far from vintage stuff from the Irish province, who were error-strewn at times, and they finally added to their 17-3 lead with a penalty try past the hour mark.
Richardt Strauss' sensational return from recent heart surgery was warmly applauded, before fellow replacements Murphy and Boss touched down to close out the bonus point win.
Leinster's round six efforts leave them in home quarter-final territory as things stand, but a Dublin date is likely to slip from their grasp by the end of the weekend.
The accurate kicking of scrum halves Eoin Reddan and Rhys Webb was an early feature, as both sides went the aerial route.
Amid some crunching hits, man-of-the-match Healy bore a hole in the Ospreys defence and a strong Leinster scrum was rewarded by three points from Gopperth's boot.
Already hampered by injuries in the back-line, the Ospreys lost the services of centre John but gritty work at the breakdown allowed Biggar to level matters - with the aid of the crossbar.
Aisea Natoga's smart break was foiled by Gopperth's penalty-winning contribution at the ensuing ruck, although the Welsh region continued to look nothing a team lying bottom of the pool.
Their task grew significantly harder when Evans was picked out by referee Romain Poite and TMO Laurent Valin for stamping on McCarthy on the ground as the Ospreys mauled forward.
The match officials agreed there was deliberate contact with McCarthy's head and the red card was produced, with the bloodied Leinster lock having to be replaced.
It was a real dog-fight up front and Leinster struggled to make their numerical advantage count as the Ospreys - despite also having to replace the influential Jones - battled for every ball.
That was until the 33rd minute when a monster lineout maul was collapsed illegally near the Ospreys line and Poite awarded a penalty try which Gopperth converted.
Biggar then got back to deny the New Zealander, positioning his leg so that Gopperth was unable to touch down under the posts following an eye-catching Martin Moore run.
But Leinster did register their second try before the break, the defensive workload taking its toll on the visitors as electric prop Healy muscled over from close range.
Gopperth converted and further injuries to Ospreys hooker Richard Hibbard and his replacement Scott Baldwin led to uncontested scrums with half-an-hour remaining.
Leinster's hunt for more tries stuttered as a Dave Kearney effort was cancelled out for a knock-on and handling errors ruined a couple of Luke Fitzgerald-inspired attacks.
The scrum became a factor again upon Marc Thomas' introduction and Ryan Bevington's move to hooker, and Leinster used to the set piece to earn their second penalty try - Webb deliberately infringing as the home pack powered up to the line.
The third try of the night was converted by Gopperth and his half-back partner Reddan just lost control of possession - under pressure from Matthew Morgan - as Leinster hunted for the fourth.
It arrived with eight minutes left as Boss' short feed was finished off by young back rower Murphy for his second try in as many European games, and Boss then gobbled up Fitzgerald's inviting pass for the fifth.
Murphy, Brian O'Driscoll, Boss and Ian Madigan all had a few bites at the cherry for a sixth try, however a couple of knock-ons let the overworked Ospreys off the hook.