The 2008 winners have been giving youngsters their chance to shine this term, but experienced lock O'Callaghan insists the mentality doesn't change.
And the 33-year-old admits the support of the Irish province's fans could make the difference as they look to secure a third European crown.
"You can't put the support we get into words, it's so appreciated by everyone at the club, we know they dig deep into their pockets and we know it's tough to come to Edinburgh and Racing but they've never dissociated themselves from us," he said.
"I know we have to go on the road, and that's our mistake, but to have 80 more minutes of Heineken Cup rugby means everything to us and everything to them.
"After the Racing Metro game this is probably the best we could have hoped for.
"The guys in the shirt may change but what it means doesn't change. We want to have a bit of legacy in the shirt and add to what the guys who have worn it before have done.
"People talk about transition, that's not the case, it means everything every week."
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