Crosby suffered the setback against the New Jersey Devils on Nov. 13 and sat for three games.
The Pens went 0-2-1 during his absence and have tumbled into a tie for last place in the Eastern Conference with the Devils at just 18 points.
While the exact nature of Crosby's injury is unclear, Penguins head coach Mike Sullivan noted it wasn't a concussion, according to ESPN.com.
Through 16 games this season, Crosby has registered eight goals and 11 assists for 19 points, placing him third on the team behind Evgeni Malkin (27 points) and Phil Kessel (24 points).
The 31-year-old Crosby is already considered an all-time great, with two Art Ross Trophies (most points in a season), two Hart Memorial Trophies (regular-season MVP) and two Conn Smythe Trophies (playoff MVP) to his credit. He's also a three-time Stanley Cup champion who has registered 1,135 points in 880 career regular-season games.
His production has waned in recent years, though, as he hasn't reached 90 points in a season since he racked up 104 in 2013-14. Crosby has finished each of the past two campaigns with 89 points.
The Pens are in the midst of one of their worst runs in recent memory, as they are on a four-game losing streak and have lost nine of their past 10 games after starting the season 6-1-2.
Pittsburgh is just two seasons removed from winning its second consecutive Stanley Cup, and it reached the second round of the playoffs in 2017-18.
Crosby will attempt to get the Penguins back on track Wednesday against the 11-8-2 Stars.