Running back Sony Michel underwent minor knee surgery, causing him to miss offseason workouts with the New England Patriots, according to multiple reports Wednesday.

A reason for his absence had not been revealed.

The date of the knee scope was not announced, but NFL Network’s Ian Rapoport said Michel should be ready for training camp next month.

Michel wasn’t seen at any of the Patriots practices that were open to the media, including minicamp last week, during the offseason.

The No. 31 overall draft pick in 2018, Michel has had a variety of knee issues. He tore an ACL in high school, then had a knee strain at Georgia in 2017.

He missed the first game of the 2018 season after having a knee procedure as training camp opened, and he missed two more games later in the year.

In 13 games, he rushed for 931 yards with six touchdowns. In three playoff games, including the Super Bowl, he had 336 yards rushing and six more TDs.