Ireland expect the returning Sergio Parisse to crank up the challenge when they face Italy on Sunday.
Parisse will finally join Italy's World Cup camp on Tuesday after missing Italy's opening two matches due to a calf injury.
The 32-year-old had remained with club side Stade Francais in Paris to be given extensive treatment on the injury, but was ruled fit enough to travel to England on Monday.
The Italy captain will now hope to complete his recovery in time to face Ireland in Sunday's pivotal Pool D battle at the Olympic Stadium in London.
Ireland can cement quarter-final qualification with victory over Italy this weekend, and know just how much of a boost Parisse's return would hand the Azzurri.
"Sergio Parisse will join the national team at morning training in Cobham," Italy confirmed in a statement.
"The captain and number eight of the national side underwent a series of final tests on Monday in Paris which showed a significant reduction of the haematoma in the calf.
"Parisse will continue treatment at Italy's training camp and, later in the week, will have his fitness evaluated ahead of the Ireland match."
Ireland eased past Romania 44-10 at Wembley on Sunday, with Keith Earls suffering a head injury scare and Rob Kearney a minor hip complaint.
"I'm sure the neutrals want to see him play but I don't know if we do to be honest!" - Devin Toner
Ireland expect Earls to be fit to face Italy after passing a Head Injury Assessment (HIA) on the side of the pitch.
"Parisse would definitely change the dynamic," said lock Devin Toner. "He controls the lineout, he owns it, he calls it: so he's a real threat if he does play.
"But he's the talisman, he spurs everything good about Italy. So if he does play it would be a coup for them.
"You never want to see players injured of course. I'm sure the neutrals want to see him play but I don't know if we do to be honest!"
Beat Italy and Ireland will qualify for the quarter-finals. See off France in turn and Joe Schmidt's men would top the pool and tee up a likely last-eight battle with Argentina.
"There's probably a bit of a mind-shift now over the next two weeks, playing two Six Nations teams in those two weeks and two teams who know us very well," said captain Paul O'Connell with Italy and France to come.
"We know them very well too and we've had very close games with France in the last two years and have been lucky enough to beat them.
"With Italy in Rome we were lucky enough to beat them too.
"It's two massive games ahead now. Parisse makes a massive difference for them, he's obviously a world-class player.
"A lot of their defensive and attacking line-outs run around him, we talked today about having 100 per cent set-piece - it's going to be a lot harder to do that against Italy.
"Around the field he can produce that something different, that maybe the teams in the last two weeks haven't had. So we've got to be ready for that."
Head coach Schmidt is under no illusions to the magnitude of the week ahead.
"This is the pivotal week," said Schmidt. "It's where we can qualify ourselves. It's pressure for us and pressure for Italy. That's why people come to a World Cup - they want to see how teams respond to the pressure cooker environment."
