The 35-year-old has not pulled on the green of Ireland since Joe Schmidt took over the role and has found his playing time at Munster limited.
But with a World Cup on the horizon at the end of this season O'Callaghan is determined to hit the ground running this time around and ensure Munster are challenging on both the domestic and European fronts.
"It's tough not getting as much game time as you'd like and the competition is fierce, so I'm not getting as many starts," he told the Irish Examiner.
"But yeah, I'm still as hungry for it, I would view it as cap one. That's all I want, to play for Ireland. "But I know playing for Ireland is as a result of going well with Munster and if we're successful here it falls out the back.
"It'll be tough, but it's World Cup year. I know myself, I wouldn't lie to myself, you have to be playing to a certain high standard to be in the shake-up and I haven't probably been at that for the last year.
"But I'm delighted to be training and being in that challenging environment."
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