Pez's calf injury opens the door for veteran Diego Dominguez to make himself available. The Argentinian-born goal-kicker pulled out of Italy's opening two Six Nations matches but scored 15 points in his comeback match for Stade Francais today.
Pez isn't the only injury headache for All Black legend Kirwan - centre Paulo Viccari lasted 17 minutes before a hip injury forced him from the field.
'We'll make a decision after a final medical, and of course we could consider to select Diego for the Welsh game,' Kirwan said.
'I thought we perfomed well in scrummaging and in the lineout during the first half but there is a lot of work to do before the Six Nations debut.'
Kirwan surprised fans by selecting brilliant backrower Mauro Bergamasco on the wing, but the move paid dividends, with the rangy flanker scoring a superb long-range try in Italy's 41-36 win over an All Stars XV.
Others to stand out included Gran Parma hooker Carlo Festuccia and lock Christian Bezzi (Viadana), who enjoyed a field-day at lineout time, but the national side were lucky to escape with the win after the referee denied Viadana's New Zealand scrum-half Harley Crane a try in injury-time.