O'Callaghan made his first start since the World Cup in the 24-19 loss to Leinster in the RaboDirect PRO12 but came off the bench in the Heineken Cup victory against Northampton.
And despite earning almost cult status at Thomond Park for his 183 caps for his province, O'Callaghan knows he can never take selection for granted.
"I always look at it like it's not my spot, I have to fight for the spot exactly like everyone else and it's great we're having this competition for places," said the 32-year-old.
"In my position anyway there's always been competition for places. I've been with Munster for 12 years and you've always said the second row spot was probably the strongest.
"We've always had great players there and now we've new young fellas again stepping up and that really makes you want to play better and fight for your place."
While O'Callaghan is still going strong alongside fellow Munster stalwarts Paul O'Connell, 32, and Mick O'Driscoll, 33, a new breed of players has emerged at Thomond Park.
Dave Foley and Ian Nagle both 23 are pushing for places in the boiler room while Peter O'Mahony, 22, is making his mark in the Munster No.7 shirt.
And O'Callaghan says the enthusiasm of the young players is rubbing off on the old guard.
"It's great. Young guys always bring new blood," he said.
"They have no fear, they haven't the scars of losing, having big games blow up in their face, they have no idea what that's like. They give everything every time, you get energy from hanging round with them."
But despite the competition for places, O'Callaghan is enjoying being back with Munster after the disappointment of Ireland's World Cup exit.
"I would have swam home, I'll be honest, to get back," he said. "You'd always play with Munster, it's just playing with your friends."
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