In passing, Mills appears to be a suitable complement alongside his backcourt mates Manu Ginobili and Marco Belinelli.
But ultimately, the Australian guard plays a pivotal role and is a noticeable upgrade from what the Spurs had during the NBA Finals run of yesteryear.
Plus, with injuries absolutely hammering San Antonio currently, Mills is arguably the most important player off the bench, and the Spurs need him to keep playing at his current level when they reach the postseason.
Offensively, Mills Is a Perfect Fit with the Top Reserve Unit
Mills, Ginobili and Belinelli are all off-ball movers, and ball rotation is the key to the reserve unit's success. With Boris Diaw essentially occupying a stretch 4 role and Jeff Ayres battling in the paint, Mills is free to move around on the offensive end.
Per NBA.com's statistical database, Mills has been assisted by Ginobili for exactly one-third (32 of 96) of his converted field-goal attempts, while Belinelli, Diaw and Ayres add 15, 14 and 10, respectively.
No, 71 of his 96 assisted baskets coming from teammates he most often plays alongside is not a surprise. But the numbers show a balanced attack, meaning Mills and Co. are not relying on a single person to facilitate the offense.
Plus, when the unit's passing is crisp and getting defenders out of position, Mills loves to slide into the left corner, and he has made 17-of-27 three-pointers from there.
And considering Belinelli paces the league and Mills ranks eighth in three-point percentage, it's difficult for opposing teams to defend multiple hot spots at once.
Defensively, Mills Does Not Have an "Off" Switch
Mills is an excellent outside shooter, but he is also an annoying—in a good way—defender.
He uses every inch of his 6'0" frame to disrupt offensive flow, and his mental awareness puts him into position to grab one steal each night.
According to NBA.com, Mills has a 97.1 defensive rating, which is 2.7 points lower than the team average. Numbers like that are often thrown around and are usually very helpful, but additional context certainly explains Mills' defensive strengths.
In mid-January, Alex Brown of the National Journal noted Mills was the league's most active player, averaging 4.8 miles per hour while on the floor.
Before the season, Dan McCarney of the San Antonio Express-News quoted head coach Gregg Popovich calling Mills "erratic," "flung around in all sorts of directions" and a player who "creates a little bit of havoc."
But that's not necessarily a bad thing, because Mills is always flying around the court, looking to make a play. If he makes mistakes, he makes them at full speed.
Of course, every player wants to avoid errors, but Mills' lapses are not due to a lack of effort.
Popovich Needs Mills to Continue Being a Perfect Complement
Former backup point guard Gary Neal's 24-point outburst during Game 3 of the 2013 NBA Finals was fun to watch.
But despite averaging 24.4 minutes per night during the seven-game series, that basically sums up his contributions against the Miami Heat. The pressure defense by Erik Spoelstra's team exposed Neal's biggest weakness to the entire NBA community—something San Antonio fans feared would happen.
Neal was effectively rendered useless as a ball-handler, and Ginobili took on responsibilities as the backup point guard.
Which as we know, save for Game 5, did not have overwhelmingly positive results.
This season, however, the trio of Mills, Ginobili and Belinelli is clearly a more complete backcourt. When one player struggles, the other two pick up the slack and keep San Antonio extremely competitive when its starters are getting rest.
Of course, injuries piling up is a legitimate cause for concern, but the Spurs should have a well-rounded team for the playoffs, and Mills is a critical piece to the puzzle.
Popovich isn't demanding the St. Mary's product be a mirror image of Tony Parker, and the effort-driven guard is not trying to be, either.
But for San Antonio to make a serious run at the conference finals and beyond, Mills must remain a perfect complement on one of the best reserve units in the NBA.
Follow Bleacher Report NBA Writer David Kenyon on Twitter @Kenyon19_BR.