The Leinster No8 feels the clash will be a tight affair and believes it will be crucial for Declan Kidneyâ€™s men to still be in contention during the latter stages of the game to have a chance of qualifying for the last four.
â€œIt will be a ding-dong battle,â€ said Heaslip. “We have played each other so much in recent times so it is reasonable to say it is 50-50.
“There will be some critical pressure moments in the match and we need to be there or there abouts in the last 20 minutes.â€
Hooker Rory Best has recovered from an injury to his right shoulder, providing a welcome boost for the Irish.
“Rory’s come up great and is fine to start the game,” said Ireland defence coach Les Kiss.
“We obviously had some precautions in place ready to cover him if he failed to pull through, but he’s in tip-top shape so full credit to him and the medics.â€
Meanwhile, Wales centre Jonathan Davies admits victory over any of his side’s local rivals is always a welcome triumph.
“We’ve played against each other so many times it’s almost like a local derby,” said Davies.
“It’s the fact that we’re pretty close, Scotland and England as well, you always want to get one up and back home the public love it as well. So it is a huge game Saturday.”
Ireland: Kearney (Leinster); Bowe (Ospreys), O’Driscoll (Leinster, capt), D’Arcy (Leinster), Earls (Munster); O’Gara (Munster), Murray (Munster); Healy (Leinster), Best (Ulster), Ross (Leinster), O’Callaghan (Munster), O’Connell (Munster), Ferris (Ulster), O’Brien (Leinster), Heaslip (Leinster).
Replacements: Cronin (Leinster), Court (Ulster), Ryan (Munster), Leamy (Munster), Reddan (Leinster), Sexton (Leinster), Trimble (Ulster).
Wales: Halfpenny (Cardiff Blues); North (Scarlets), Jonathon Davies (Scarlets), Roberts (Cardiff Blues), Shane Williams (Ospreys); Priestland (Scarlets), Phillips (Bayonne); G Jenkins (Cardiff Blues), Bennett (Ospreys), A Jones (Ospreys), L Charteris (Dragons), A Wyn Jones (Ospreys), Lydiate (Dragons) Warburton (Cardiff Blues, capt), Faletau (Dragons).
Replacements: Burns (Dragons), James (Ospreys), B Davies (Cardiff Blues), R Jones (Ospreys), L Williams (Cardiff Blues), Hook (Perpignan), Scott Williams (Scarlets).
MORE: The latest football news
MORE: The latest tennis news