But after his run-on as a replacement against Italy and assured performances as a starter against France and Scotland, the 24-year-old has quickly knitted himself into the fabric of the team.
Speaking at the team hotel in Killiney this week, he reflected: "I suppose if you look at the number of caps (I have) you might think I am still finding my feet, but this is my second Six Nations championship in terms of being around the extended squad and I have also been in various camps.
"I think I'm comfortable in this environment and enjoy the company on and off the pitch.
"I've found the step up to international level okay, it's note a huge jump. The only game that was fast was the first 20 minutes of the France game, which was like lightning.
"But apart from that I've been okay and I feel I have adjusted well to the pace."
Heaslip's most prominent play to date in this year's Six Nations was his assist for David Wallace's try in Ireland's 34-13 win over Scotland last time out, which saw him peal off a scrum and flick an inside ball for the onrushing flanker.
Commenting on that training ground-manufactured score, which harked back to previous eras, the Kildare man said: "The coaches and Merv (Murphy), the video analyst, spotted that. We had a look at it and that was the plan. It's an old move and I remember my dad saying he used that move about 20-odd years ago.
"We saw that the Scots wedged a little bit too hard at times, especially with Redser (Eoin Reddan) posing a threat, and it worked for us.
"We said let's have a go because it's on and Wally (David Wallace) was in under the posts.
Like many of his Ireland team-mates, Heaslip has been pressed this week for his opinion on the all too obvious sub-plot to tomorrow's showdown with Wales - the coaching head-to-head between Eddie O'Sullivan and Warren Gatland, his predecessor in the Ireland job.
Heaslip was as frank as ever when admitting: "The players don't take any notice of it. There's no point because everything is out of your hands.
"I've never been coached by Warren so I can't comment on anything like that. There's obviously a bit of history there but it's nothing really.
"I have met Warren before. My brother Graham was captain at Connacht when Gatland was coaching there.
"I met Warren in the back of a car after a Connacht game. That was it. I said 'hi' to him and then shut up because I didn't really know who he was. Graham later told me who he was.
"I just wanted to play and wasn't too concerned about what was going on. It was more my dad pestering Graham with questions about Warren. But he doesn't seem such a bad fella."
Heaslip will have his own head-to-head to deal with on the pitch tomorrow as his direct opponent will be Ryan Jones, the Welsh captain.
"I played against him once last year but I know the sort of havoc he can cause. I'll definitely do my homework on him because he's a handful alright," conceded the Leinster tyro.
"I've been looking at him on TV and there's no doubt he'll cause some problems for us in the back row. But if I'm on top of my game then hopefully I'll be able to keep him somewhat quiet."