The Munster player took part in a training session on Thursday and will now pack down in the Irish front row in Rome.
"Marcus is fine. He had a run-out this morning and so far everything is good. We are 95 percent sure he will be right for Italy," said Ireland coach Eddie O'Sullivan.
"Obviously, something could flare up overnight, but today I'm happy with his fitness."
Ireland go into the game knowing a win could give them the title for the first time in 22 years but they are dependent on the France and Scotland and Wales versus England results.
Ireland: Girvan Dempsey (Leinster); Shane Horgan (Leinster), Brian O'Driscoll (Leinster, capt), Gordon D'Arcy (Leinster), Denis Hickie (Leinster); Ronan O'Gara (Munster), Peter Stringer (Munster); Denis Leamy (Munster), David Wallace (Munster), Simon Easterby (Llanelli), Mick O'Driscoll (Munster), Donncha O'Callaghan (Munster), John Hayes (Munster), Rory Best (Ulster), Marcus Horan (Munster).
Replacements: Jerry Flannery (Munster), Simon Best (Ulster), Trevor Hogan (Munster), Neil Best (Ulster), Eoin Reddan (Wasps), Paddy Wallace (Ulster), Andrew Trimble (Ulster).