49ers linebacker Reuben Foster is one of the biggest NFL preseason winners of 2017

Two weeks ago, San Francisco 49ers rookie linebacker Reuben Foster was arrested in Alabama on marijuana charges.

His league punishment has yet to be decided, but general manager John Lynch issued a warning while expressing what he expects of Foster moving forward.

“He’s got to stay — he knows it — he’s got to stay clean, Lynch said, per Jennifer Lee chan of ninersnation.com. We all know how special of a player he can be when he’s right. So he’s got to figure out how to stay healthy and stay out of trouble, but we believe he will do that.”

Lynch also said that the team has “probably spent more time with him than anybody in the draft.” The 49ers traded up to draft Foster 31st overall in 2017. He has proved to a valuable addition to a San Francisco defense that ranked worst in the league in 2016.

In the 10 games Foster played in 2017, he racked up 72 combined tackles, which accounted for the second-most of any 49ers defender.

The team can only hope that Foster’s run-in with the law will be an isolated incident.