The 32-year-old midfielder abandoned Thursday's practice session after complaining of a muscle problem.
It is believed that Pirlo will undergo a series of tests before the end of the day to determine the extent of the injury and learn whether he will be available for the upcoming match at the Stadio Olimpico.
Pirlo's absence would come as a heavy blow to boss Antonio Conte, who has used the ex-AC Milan player in every match this season so far.
Juventus and Lazio are sharing the top of the Serie A standings, on 22 points, although the Turin-based side have one game in hand.
How do you stay up with football when on the move? With http://m.goal.com –your best source for mobile coverage of the beautiful game.