4. Amik Robertson, CB, Detroit Lions
Amik Robertson was a bit of a polarizing figure in his tenure with the Raiders.
Every offseason, it seemed like fans wanted him gone or buried on the end of the roster.
But every year, Robertson found his way into the lineup and balled out. He had a knack for making big plays and was solely responsible for clinching several games.
However, he was left to walk in free agency and chose to sign with the Detroit Lions.
Robertson has made quite an impact, playing just over half of the team's snaps and recording 34 tackles, including three for a loss, four pass deflections, and two forced fumbles.
While the Raiders do have a solid trio of cornerbacks, their depth has been tested quite a bit this season.
Instead of re-signing Robertson, Telesco chose to draft Decamerion Richardson in the fourth round, who missed the first six weeks due to injury, and sign Brandon Facyson, who ended up being cut from the initial roster.
Letting Robertson go is probably Telesco's second-biggest regret. At least Robertson may get a Super Bowl ring out of the deal.