Munster's captain Paul O'Connell, also a 2005 Lion, even declined a kickable penalty with 90 seconds left because it risked handing possession back to Toulouse, who had already served notice of their potential to create a try from nothing.
Instead, Munster took the quick tap and kept the ball at close quarters, eating up the seconds until referee Nigel Owens blew up to confirm their second European title.
"It may be boring but who cares?" said O'Callaghan, his face scarred and body sore from a fierce forwards encounter.
"I have got a medal in my pocket."
It was the 10th of 13 European Cup finals to be decided by less than a converted try and O'Callaghan believes Munster, under the stewardship of Declan Kidney for the last time, were better prepared for such a contest.
The Munster forwards won crucial collisions at the breakdown and in the scrum, successfully disrupting Toulouse's possession, and Jean-Baptiste Ellisalde was made to look exactly what he is - a stand-in fly-half.
Munster came roaring into the game after a slow start and Denis Leamy pounded over the line to earn a narrow 10-6 half-time lead.
The match seemed to be turning Munster's way when Toulouse captain Fabien Pelous was sin-binned for aiming a petulant kick at the magnificent Alan Quinlan.
But despite being down to 14 men the French giants drew level at 13-13 when a dash of brilliance from Cedric Heymans created the opening for winger Yves Donguy to score.
Pelous returned but was penalised again, this time for not rolling away in the tackle, and Ronan O'Gara landed his third penalty of the day to earn Munster the vital final advantage.
Munster then turned the screw to give Kidney, who takes over as Ireland coach later this summer, and Australia-bound assistant Jim Williams the perfect send-off.
"It's incredible," said O'Callaghan. "We knew it was going to come down to small margins. The thing is that you learn from experience from the tight games you play like this before.
"It comes from playing in the All Ireland League, schoolboy rugby and how to win it out. It might be boring but who cares? It is effective for us.
"There was just such a great sense of belief even when we were behind the posts after their try. We looked around and there was that belief that we were not going to lose.
"It's great that we are sending the coaches off on the biggest high possible."