She noted all of the changes Ireland had made to the side that had started the game as a potential reason for the score conceded in the second half, and claimed concentration came be a problem in games when a side is winning comfortably, as "it's hard sometimes to build yourself up when you're winning by so much".
Ireland's 56-19 victory over Italy at the Aviva Stadium sets them up nicely for the visit of Wales in two weeks time.
Italy lost out 46-15 to England in Rome last weekend in their opening Six Nations clash.
Quaglio, after three appearances off the bench, comes in for Andrea Lovotti while Steyn replaces youngster Renato Giammarioli in a strengthening of the scrum.
Italy for their part fought to the end, scoring three second-half tries but slipped to their 14th successive Six Nations defeat, equalling their previous worst run in the tournament.
The Azzuri struggled to keep the hosts at bay and a third try came midway through the first half when imposing centre Bundee Aki showed formidable strength to outmuscle two Italy defenders and power through to score.
Ireland led in the 11th minute when Connor Murray's smart pass found Robbie Henshaw and he crashed over from close range.
Aki then turned creator as he made a terrific break to set up Keith Earls to go over to seal the bonus point and Sexton converted to send the Irish in 28-0 up at the break.
Henshaw's potential absence would leave Ireland vulnerable in midfield where they were already without Garry Ringrose, although Schmidt said the young centre was making really good progress recuperating from an ankle injury and has a shot at returning for Leinster during next weekend's Six Nations break. "We've got a scan booked for him".
What TV channel is Ireland vs Italy on and can I live stream it?