McClain (6-foot-2, 300 pounds) was a third-round pick of the Panthers last season. The 24-year old South Florida product started 12 games last season, tallying 19 tackles and one sack, before being placed on injured reserve with a sprained left knee.
Forston was an undrafted free agent signed by the Patriots in May out of Miami. He made his NFL debut on Sunday night in Baltimore, playing eight defensive snaps.
The Patriots were without defensive tackle Brandon Deaderick (ankle) for their loss in Baltimore, so swapping McClain for Forston could give the team a more game-ready player if Deaderick is out for an extended period.