Ireland captain Rory Best will miss the RBS 6 Nations match against Italy in Rome due to illness, the Irish Rugby Football Union has announced.
Best has failed in his bid to shake off a stomach bug in time to lead Ireland in their second Six Nations clash of the 2017 tournament, so Jamie Heaslip will skipper Joe Schmidt's side.
Niall Scannell will start with James Tracy on the bench.
The match is due to start at 2.25pm in Rome.
Ireland must win in Rome to keep alive any slender title hopes following last weekend's 27-22 loss to Scotland at Murrayfield.
Ulster stalwart Best missed Ireland's captain's run training session on Friday in a bid to rest and recuperate from his illness.
But now the 101-cap front-rower will sit out Saturday's pivotal clash with Conor O'Shea's Azzurri in Rome.
Scannell was an unused replacement in Edinburgh, but is now thrust into the spotlight.
Ireland unusually struggled at the lineout last weekend, so Scannell must quickly organise his set-piece work with lock Devin Toner.
Leinster's fast-improving hooker Tracy won his first cap against Canada in the autumn, and may well join the fray in the final quarter.