But the 32-year-old has returned to club duty at a Munster side that currently sit second in the RaboDirect PRO12 table, eight points behind runaway leaders Leinster.
And with a home play-off semi-final up for grabs, the 85-cap man insists his teammates at the Red Army have played a key role in picking him up after the disappointment of the Six Nations.
"Leinster are a quality opposition so it has been a tough week," he said. "It really bangs it home that you have to be on top of all the little details since coming back from Ireland and getting back into Munster colours.
"It's been great, there's a huge appetite for work at this club and the standards are really high so you're getting back and the work ethic is already in place.
"It would be hard to make that shift back to Munster if the standards weren't so high, you would be coming back and dragging the disappointment of the Six Nations with you.
"But you get back and the lads here pick you up and drag you along, they know you're hurting but the momentum is building here and that's all we want."
Table toppers Leinster recently had their 20-game unbeaten run come to an end at the hands of fellow high flyers Ospreys.
But despite that slight hiccup O'Callaghan insists none of his teammates are taking their arch-rivals lightly when battle commences at Thomond Park on Saturday.
"Leinster are the standard setters at the moment and the big thing really from a forward's point of view that we are targeting is the breakdown," he added.
"They are particularly strong there so we need to be spot on in that aspect, it's an area we have highlighted but in truth when looking at a team like Leinster you could pick out any aspect of their game as a strong point."
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