Porter, 27, signed a one-year contract with the Raiders last year after spending just a single season with the Broncos in 2012.
He has dealt with some concussion issues in recent years, however, he managed to play in all 16 games for the Raiders last season. Porter totaled 66 tackles, 1.5 sacks and an interception.
Pro Football Focus had him rated as the No. 105 cornerback out of 110 qualifying players.