The lock was part of the side that had to ride their luck before emerging 21-20 victors against Irish rivals Ulster last weekend, a fifth consecutive league win.
O'Callaghan, who was cited for allegedly kicking Stuart Olding during the clash, will now welcome back Paul O'Connell into the second row for back-to-back European clashes with Clermont.
And with the seven Irish internationals in total returning to the fore, O'Callaghan has a battle on his hands to retain his starting place.
"We need to improve. I know we're playing in Thomond but that might not be enough if you've a slow start like that," O'Callaghan admitted.
"I suppose there were areas of it that you would be happy with, maybe the breakdown, but I'll be honest, when you're in the row you need to watch the game again.
"I'm not sitting on the fence but I had my head between two arses for the day and I didn't get to see. I'm not taking away from it but I know there will be improvements and things to work on. It's nice to reflect on the nice bits but they won't be in our review all that much.
"I want to be in the team. I'm not saying I'm a nun or anything. They've my full blessing but I'm competitive. I want to go well but it's all about us getting a result and I'm going to do whatever it takes for that to happen.
"But you're bringing back quality players and they're on the top of their game at the moment so hopefully they can bring that little bit of intensity."
Follow us on Facebook, join the conversation on Twitter, sign up to our YouTube channel for extensive match highlights and sign up for our newsletter for regular updates on the GUINNESS PRO12
Guinness PRO12
Suite 208, Alexandra House,
The Sweepstakes
Ballsbridge, Dublin 4, Ireland