For Davis, it's the third time he has been promoted to the practice squad, as he's expected to fill the special-teams role created by Cole's release. It's possible that Cole was released for health reasons, as was the case when he was waived earlier this season.
Green has also spent time on the active roster this season, playing in one game. He provides insurance in the secondary as well, adding depth to the cornerback spot. Each of the Patriots' top three cornerbacks has dealt with injuries of late.