Guentzel suffered the injury during the third period of Monday's 5-2 win over the Ottawa Senators. After scoring his 20th goal of the season, Guentzel was tripped and went crashing into the boards:
The 25-year-old Guentzel leads the Penguins in goals (20) and points (43) this season, and he was selected as the team's lone All-Star representative.
With Sidney Crosby currently on the shelf and having been limited to 17 games this season due to surgery to repair a core muscle injury, Guentzel has stepped up to become Pittsburgh's top offensive weapon.
Guentzel's first true breakout came during the 2017 Stanley Cup playoffs when he posted 21 points in 25 games. He followed that up with just 48 points in 82 regular-season games the following year but recorded 21 points in 12 playoff contests.
The Omaha, Nebraska, native finally came through with a productive regular season in 2018-19 when he scored a career-high 40 goals to go along with 36 assists for 76 points in 82 games.
Guentzel had been on pace to exceed last season's production, but it is unlikely he will play another game until the playoffs at the earliest. The best-case scenario based on the timeline given by the Penguins is that Guentzel will return at the end of April, which would be in the midst of the postseason.
With Guentzel out, Penguins head coach Mike Sullivan will need a number of different players to step up and replace his production.
The most obvious name is Evgeni Malkin, who is second on the team in scoring with 38 points and first in assists with 27 in just 26 games. Bryan Rust must also keep up his hot streak, as he has 16 goals and 16 assists for 32 points in 25 games.
Jared McCann, Dominik Kahun and Brandon Tanev are other forwards who will be tasked with taking on greater roles.
Alex Galchenyuk has arguably been the Penguins' most disappointing player this season with 13 points in 30 games, but he has three points in his past three games and must play significantly better to help offset Guentzel's loss.
Even with all the injuries to key players this season, the Penguins have persevered and are currently second in the Eastern Conference's Metropolitan Division with 52 points.