Ian Rapoport of NFL Network updated Mahomes' status ahead of Sunday's AFC Championship Game and noted Mahomes will see a specialist after the season to determine if surgery is needed.
Later on Sunday, Jay Glazer of Fox Sports said Mahomes was fitted with a custom orthotic to helped deal with the injury.
Mahomes, 25, has completed 66.1 percent of his passes for 114 touchdowns and just 22 interceptions in 45 regular-season games since becoming the Chiefs' full-time starter in 2018. His resume includes the 2018 MVP and a Lombardi Trophy after Kansas City defeated the San Francisco 49ers to win Super Bowl LIV in February 2020. Mahomes won the Super Bowl MVP for his efforts as well.
His 50 passing touchdowns led the NFL in 2018, and his 316.0 passing yards per game paced the league in 2020.
Mahomes is on a trajectory to become arguably the NFL's greatest of all time, and losing him for any snaps is a tremendous blow for the Chiefs, even if the roster is stacked with talent.
He has missed time before after suffering a dislocated patella while attempting a quarterback sneak against the Denver Broncos in October 2019. He missed the remainder of that game and two more before returning in Week 10 against the Tennessee Titans. Matt Moore took over behind center until Mahomes returned.
Mahomes played all 16 regular-season games in 2020 but exited his team's AFC Divisional Round win over the Cleveland Browns after suffering a concussion following a tackle from linebacker Mack Wilson. Mahomes, who was also dealing with a left big toe injury suffered in the first quarter, was forced to leave the game.
Veteran backup Chad Henne took over for Mahomes in the AFC Divisional Round.
Henne's most extended action with the Chiefs came when most of the team's starters rested during a 2020 regular-season finale against the Los Angeles Chargers with the AFC's No. 1 seed locked up beforehand. He went 23-of-32 for 218 passing yards and two touchdowns in a 38-21 loss.
The 35-year-old, who spent time with the Miami Dolphins and Jacksonville Jaguars from 2008-2017 before joining Kansas City in 2018, went 6-of-8 for 66 passing yards and one interception against the Browns when he entered the AFC Divisional Round Game for Mahomes.
Henne closed the door down the stretch, however, helping convert a 3rd-and-14 into a game-sealing first down thanks to a 13-yard run and a five-yard toss to Tyreek Hill. The Chiefs then went into victory formation to advance to the AFC title game for the third straight year.
Versus the Bills, it seems unlikely we'll see Mahomes on any designed runs, and his mobility in the pocket may be affected.