Schmidt, though, already has extra cover in the midfield, having freed up a space for the Ulster centre Darren Cave in going with only two recognised halfbacks.
Isaac Boss and Kieran Marmian will remain on standby with Ian Madigan now covering both halfback positions.
"I'd like to think it's a calculated risk," Schmidt said. "We've given it as much thought as we could. Isaac [Boss] did very well against Scotland. That physical aspect of his game is something we'll miss. To a degree, that risk is managed by the 48-hour rule and the opportunity to get someone in within that time frame before a match if there is an injury.
"Ian has done a lot of individual training [at halfback], but it's only in the last week he's started to slot in and do a little bit at 9 with the team. I spoke to Ian about it last season, so it's not suddenly something that's sprung up."
Cave will provide cover for the first-choice centre pairing Jared Payne and Robbie Henshaw, while the wingers, Keith Earls and Luke Fitzgerald, who were injured during the defeat by Wales in Dublin on Saturday, are also included.
Simon Zebo, Earls, Fitzgerald and Payne all provide fullback cover for first-choice No15 Rob Kearney, with Munster's Felix Jones, Leinster's Fergus McFadden and Ulster's Craig Gilroy all missing out.
Ireland squad
Backs: Rob Kearney, Tommy Bowe, Luke Fitzgerald, David Kearney, Simon Zebo, Darren Cave, Keith Earls, Robbie Henshaw, Jared Payne, Paddy Jackson, Ian Madigan, Jonathan Sexton, Conor Murray, Eoin Reddan
Forwards: Jamie Heaslip, Chris Henry, Jordi Murphy, Sean O'Brien, Peter O'Mahony, Iain Henderson, Paul O'Connell (c), Donnacha Ryan, Devin Toner, Rory Best, Sean Cronin, Richardt Strauss, Tadhg Furlong, Cian Healy, Jack McGrath, Mike Ross, Nathan White