Having left Ramiro Pez, Italy's number 10 during the World Cup, out of his squad, Mallett said: "We've got to start somewhere. The number 10 position has been a problem in the past. The sooner I see Masi playing the better and the sooner he will improve. He'll be there for the next three games.
"I'm trying to introduce more variety, to do that I need a back-line that can be dangerous and can threaten. I've picked a number 10 that can do that. You can't always go for safety first."
In all, there are five changes to the Italian side that started their 18-16 loss to Scotland in their final World Cup pool game in September. As well as the switches at half-back, hooker Leonardo Ghiraldini, who will be making his Six Nations debut, and prop Andrea Lo Cicero come in to replace Carlo Festuccia and Salvatore Perugini, while Masi's place on the left wing has been taken by Castres clubman Pablo Canavosio.
There is an experienced edge to the Italian pack, with Lo Cicero (71 caps) being joined in the front row by Martin Castrogiovanni (49 caps), Ulster's Carlo Del Fava is a familiar face in the second row, while Stade Francais back rower Sergio Parisse will be leading his country for the first time.
ITALY TEAM AND REPLACEMENTS (v Ireland, 2008 RBS 6 Nations, Croke Park, Saturday, February 2, kick-off 2pm):
15 - David Bortolussi (Montpellier)
14 - Kaine Robertson (Viadana)
13 - Gonzalo Canale (Clermont Auvergne)
12 - Mirco Bergamasco (Stade Francais)
11 - Pablo Canavosio (Castres)
10 - Andrea Masi (Biarritz Olympique)
9 - Pietro Travagli (Overmach Parma)
1 - Andrea Lo Cicero (Racing Metro)
2 - Leonardo Ghiraldini (Calvisano)
3 - Martin Castrogiovanni (Leicester Tigers)
4 - Santiago Dellape (Biarritz Olympique)
5 - Carlo Del Fava (Ulster)
6 - Josh Sole (Viadana)
7 - Mauro Bergamasco (Stade Francais)
8 - Sergio Parisse (Stade Francais) (capt)
16 - Carlo Festuccia (Racing Metro)
17 - Salvatore Perugini (Toulouse)
18 - Carlos Nieto (Gloucester)
19 - Tommaso Reato (Rovigo)
20 - Alessandro Zanni (Calvisano)
21 - Andrea Marcato (Benetton Treviso)
22 - Ezio Galon (Overmach Parma)