Bryant sustained the injury while running to first base during the third inning of a 3-2 loss to the St. Louis Cardinals on Sunday. The three-time All-Star and 2016 National League MVP stepped on the base, which was wet from rain, and lost his footing, before falling into the infield dirt. Cubs trainers tended to him before he left the game.
Bryant had an MRI on Monday to determine the extent of the injury, but the team has not revealed the results of the scan. The Cubs star already was playing with a right knee ailment.
Philadelphia Phillies slugger Bryce Harper, another Boras client, sustained a hyperextended knee and bone bruise when he slipped on first base during a 2017 game with the Washington Nationals. Harper didn't return until the last week of the season.
"What has [MLB] done since Harper? The answer is, nothing," Boras told the Chicago Sun-Times. "They're focused on other factors, economic factors, all things relating to how they can administer the game, and yet the safety of players and resolution of this issue has gone without any attention.
"The integrity of our game is going to [be] damaged when the safety of players is not at the forefront, and Major League Baseball has dropped the ball on the wet-bag subject."
Boras said players and teams are in between collective bargaining agreements and shifted responsibility to MLB commissioner Rob Manfred.
"The office of the commissioner has the authority to legislate matters of the game relating to weather. ... We were put on notice about this issue years ago," Boras told Sports Illustrated. "Where is the protocol for it? It borders on negligence. They did nothing. Zero."
MLB protocol gives umpires the ability to determine if a field is safe. Umpires can direct members of stadium grounds crews to tend to pitcher's mounds and more, but there is no specific rule about the condition of bases.
Bryant, 27, has a $12.9 million salary and is eligible for arbitration in 2020. Boras helped Harper land a 13-year, $330 million pact with the Phillies in February.
The Cubs (82-74) are 7 1/2 games out of first place in the National League Central division and four games behind in the National League Wild Card race. Chicago has are six games remaining in the regular season entering a three-game road series against the Pittsburgh Pirates.
The Pirates host the Cubs in the first game of the division series at 7:05 p.m. EDT Tuesday at PNC Park in Pittsburgh.