The Buffalo Bills agreed to terms Saturday to re-sign starting right tackle Jordan Mills, making him the second of the Bills' 22 unrestricted free agents to return to the team.

Here is more on the deal:

Terms: Two years, $4 million (per ESPN NFL Insider Adam Schefter)

ESPN 150 ranking: No. 150

Grade C-plus: In a perfect world, the Bills surely would have liked to upgrade at right tackle this offseason. Former NFL executive Michael Lombardi tweeted earlier this week that the Bills were "all over" free-agent tackle Rick Wagner, who later signed with the Detroit Lions. The Bills also hosted free agent Andre Smith on a visit Saturday, a source told ESPN's Jeff Darlington. In the end, the Bills likely saw Mills as their best option in a thin free-agent market at tackle and decided to fill their void with a player they know well.

What it means: The Bills are not making a huge financial commitment to Mills, but it is a pay raise from his previous deal (one year, $1.671 million) and makes him the favorite to earn the starting right tackle job again next season. Former second-round pick Cyrus Kouandjio finally showed promise last season as a fill-in at left tackle when Cordy Glenn was injured, but he appears to be a better fit on the left side than the right side. The long-term status of Seantrel Henderson is also uncertain as he serves the remaining five games of a 10-game suspension to start next season. The Bills also signed former Jets and Ravens lineman Vladimir Ducasse to a deal this week, but he projects as a backup at both guard and tackle.

What’s the risk? Mills was a liability at times last season, ranking 64th among NFL offensive tackles in Pro Football Focus' grading. He notably struggled against Oakland's Khalil Mack in a Week 13 loss to the Raiders, allowing quarterback Tyrod Taylor to be pressured on two critical plays -- an interception when Mack hit Taylor's arm, as well as a strip-sack to seal the defeat. While Mills could be valuable as a backup/swing tackle in the NFL, it is debatable whether he provides starting-level play. With the free-agent market and draft class thin among offensive tackles, he might be the Bills' best option at this time -- but that's not saying much.