Ireland have refused to gamble Johnny Sexton's Six Nations fitness on Saturday's tournament-defining encounter with Italy in Rome.

Lose at the Stadio Olimpico and Ireland would concede any lingering title chances, but boss Joe Schmidt has refused any temptation to field his linchpin fly-half.

Sexton missed the 27-22 loss in Scotland with calf trouble and was only ever handed an outside chance of facing Italy, so head coach Schmidt has again turned to Paddy Jackson to run his backline.

Sexton has not played since Leinster's 24-24 draw at Castres on January 20, but Ireland still expect the 31-year-old to be ready to face France in Dublin on February 25.

The fit-again Donnacha Ryan replaces Iain Henderson at lock after Ireland missed the Munster man's wily tight work in Edinburgh.

Ryan and Cian Healy slot in to start in the only changes from the galling Scotland defeat, with Ireland's Kiwi boss Schmidt challenging the bulk of those players to provide immediate atonement.

Connacht's Ultan Dillane is preferred to Henderson as the lock cover on the bench, with Ulster wing Craig Gilroy also named among the replacements.

Schmidt has laid down the gauntlet to Ireland to move out of any professional era comfort blanket and cope far better with unexpected setbacks.

Ireland's bus was 15 minutes late arriving at Murrayfield last Saturday, with Schmidt later admitting his players were unsettled by a rushed warm-up.

Now the former Leinster coach has demanded his players quickly devise far better coping strategies for similar unforeseen issues.

Loading....

"I have challenged them for a better start in Italy," said Schmidt.

"I think it's incredibly disappointing the way we started last weekend.

"I don't think it was apathy, there was a bit of anxiety at not having had the full period to warm up.

"Players get anxious, they get very routine-based and I do think it's a challenge for a professional player that they can be adaptable in different circumstances, so they can still start well and cope.

"We were really disappointed with the way we started.

Ireland were poor in the first half against Scotland (Getty)

"They scored three tries in those first 25 minutes, then didn't score another try after that.

"And I think that reflects what the team were capable of, but unfortunately then you're chasing things.

"So we've certainly given them that challenge this week, and hopefully we see a better start."

Ireland team to face Italy: R Kearney (Leinster); K Earls (Munster), G Ringrose, R Henshaw (both Leinster), S Zebo (Munster); P Jackson (Ulster), C Murray (Munster); C Healy (Leinster), R Best (Ulster, capt), T Furlong (Leinster), D Ryan (Munster), D Toner (Leinster), CJ Stander (Munster), S O'Brien, J Heaslip (both Leinster).