5. Derrick Jones Jr.
Derrick Jones Jr. was likely Dallas' second most beneficial free agent acquisition behind Dante Exum. Jones Jr. has been one of Dallas' best defender this year, as the 6-foot-6 wing uses his length extremely well when guarding opposing guards and wings. Despite this being his eighth year in the league, Jones Jr. doesn't turn 27-years-old until February 15 of this year which may surprise some Mavericks fans.
Jones Jr. fits Dallas' timeline well, and he's molded himself into a player that Dallas should be looking to retain next year, after he signed a one-year veteran's minimum deal with Dallas this past summer. Jones Jr. has played excellent on-ball defense for Dallas as aforementioned, and he hasn't backed down from having to guard bigger wings when tasked with the assignment.
Jones Jr. has been extended past his means a few times this season on defense because of Dallas' lack of lengthier wings, so hopefully that hasn't attributed to the recent minor injuries that have kept him in-and-out of the lineup throughout January. Nonetheless, Jones Jr. has been a great help-side defender for Dallas as well, as he uses his athletic tools well and stays in position when off-ball.
A far more surprising development for Jones Jr. this season though has been his offense. Jones Jr. is averaging a career high 10.1 points per game on 48.6/34.9/73.7 shooting splits. Jones Jr. has showcased a dribble-drive game in Dallas that hasn't been on display near as much in his other NBA stops, and he's surprisingly been a crafty finisher and decent driver off the catch. Jones Jr. is shooting the best mark from three-point land in his career, but his shot looks like it has regressed some recently.
Jones Jr. has been an excellent cutter as well for Dallas, but he needs to rekindle some of the flow that he had to his offensive game early in the season, as he has looked a lot more hesitant on that end recently. Jones Jr. finishes with a B+ through 47 games.