The Thunder have agreed to sign defensive-minded guard Cason Wallace to a five-year rookie-scale extension worth $139MM, Shams Charania reports for ESPN (via Twitter).

The move comes one day before the October 19 deadline for rookie-scale extensions, and signifies a major investment in the All-Defense guard, who is likely to inherit the starting shooting guard role left open when the team traded Luguentz Dort to the Hawks.

While Wallace’s scoring output stayed steady last year, going from 8.4 points per game as a sophomore to 8.6 as a third-year guard, he solidified himself as one of the best perimeter defenders in the league, leading the NBA in total steals and deflections and coming in third in steals per game.

For his efforts, Wallace was named to the All-Defense Second Team and came in seventh in Defensive Player of the Year voting.

Wallace is also a career 37.4 shooter from three, and should help to provide even more spacing to the Thunders’ offensive creators such as Shai Gilgeous-Alexander and Jalen Williams. While Dort has had years where he shot extremely well from three, Wallace is likely to be guarded as more of a threat by opposing defenses.

Oklahoma City now has all five starters on multi-year deals, in addition to depth pieces like Alex Caruso, Bennett Stirtz, and Aday Mara. They will likely face a huge luxury tax bill next summer, Keith Smith of Spotrac notes (via Twitter), but the move keeps Wallace at a fair price before he hits the open market, while also eliminating a possible off-court source of distraction.