Jaren Jackson, Jr. is very likely to end up a top 10 pick next draft. The Michigan State big man already looked great on paper, possessing elite measurements and only turning 19 next September, but he has still managed to increase his draft stock by what he's achieved on the court as well.
Jackson has impressed many observers over the first month of the season, proving himself to be a very effective rim protector while showing flashes of three-point range on the other end. In an era where every team is looking for a big who can simultaneously space the floor and be a plus of some sort on defense, Jackson should be highly regarded.
He projects as a player who should spend a lot of minutes at center in five-out lineups that stretch the opposing defense to its breaking point, but he's yet to be used in that way. Jackson has played almost all of his minutes at Michigan State with another true big man in the lineup as well, with the only exception I’ve seen so far being a couple minutes against Southern Utah on Saturday.
The Spartans run a lot of stuff that is mid-post oriented, with the wings sprinting around down screens for catches on the side of the floor or the big men facilitating from the elbow, but there have also been plenty of opportunities for Jackson to screen for pick-and-pops and space out to the three-point line as a weak-side spot-up shooter. He’s also received the ball with his back to the basket some.
Jackson is supposed to be a finisher of possessions, whether it’s at the rim, from three-point range or on emergency post-ups late in the clock, but his 24.3% usage rate  is quite robust for someone whose role is not to put up a lot of shots and has provided a good chance to get a decent feel for the things he does well or needs to improve on at this point of his development.
Defensively, Michigan State consistently has him on the lighter of the opposing big men. He is currently listed at 242 pounds, some 17 pounds heavier than he weighed at the Nike Hoop Summit, but he's yet to show a whole lot of reliability in terms of engaging in the most physical aspects of the game.
Jackson has proven himself to be an exceptional asset in areas more related to movement and activity. His combination of nimbleness for someone his size and length were already very appealing on paper but he’s translated them into production in pick-and-roll defense extending far beyond the foul line, and in help defense by playing with the sort of intensity you don’t necessarily see from guys with his physical attributes.
Jackson's shot blocking has been his most impressive attribute.
The six-foot-10 big has a nine-foot-one standing reach and has shown phenomenal leaping ability, whether it’s off one foot rotating from the weak-side in help-defense and sprinting back in transition, or off two feet after keeping pace with dribble drivers as they turn the corner off the pick-and-roll.
Putting in the effort to consistently try challenging everything he is close by, Jackson has averaged 5.4 blocks per 40 minutes so far this season. His 75.4 defensive rating ranks third in the country .
The downside of all that intensity is that Jackson is often putting himself in risk of contact that is up for interpretation, aside from the fact that he is prone to biting on shot fakes, which have resulted in him averaging 5.9 personal fouls per 40 minutes – limiting his playing time to just 22.4 minutes per game so far.
Jackson has made some preventive rotations that clog up driving lanes, plays that suggest there is some pretty good defensive awareness there to be developed. He is not yet the sort of rim protector who keeps opponents from getting to the basket in the first place all that often, though.
The other issue with his interior defense is rebounding. He is rarely inattentive to his box out responsibilities but hasn’t shown an inclination for getting physical in his attempts to erase the opponent off these plays.
Jackson is a quick leaper who consistently chases the ball off the rim proactively, which explains the fact he’s picked up 24.1% of opponents’ misses against what ranks as the 70th toughest schedule in the country  so far, but it’s not uncommon to see him giving up second chance opportunities that figure to become a more tangible problem as they enter conference play.
His mobility and coordination afford his coach a variety of options on how to use him against the pick-and-roll.
Jackson has been asked to extend out to the top of the key consistently, either hedging or showing-and-staying-out-an-extra-second to try preventing the ball handler from turning the corner right away or getting to the middle on side pick-and-rolls.
He’s shown he can slide laterally very fluidly to execute that strategy out in space, aside from being able to stay attached to the guards who have tried driving around him just the same and follow wings who curl around pindown screens, at least well enough to use his length to challenge or scare away shots at the basket, showing himself attentive enough to guard with his arms raised in these instances.
Michigan State has asked that of him even against shooting threats setting the ball-screen, banking on his quickness to hustle back to the shooter in time to run him off the three-point line or at least contest the catch-and-shoot jumper effectively. He hasn’t forced many guys to put the ball on the floor, but consistently puts in the effort to contest these shots as well as you can expect, given how tough the pick-and-pop is to defend.
Southern Utah burned Michigan State on a couple of those, which forced Tom Izzo to have his team switching on screens over the final eight minutes. Jackson doesn’t really bend his knees a whole lot to get down in a stance but has good lateral quickness to keep pace with smaller players stride for stride.
Given his athleticism, he projects as someone who should be an asset to switch on these players and stay in front out on an island or track them on the move as they catch it on hand-offs and off a live dribble. There were some possessions in the game against North Carolina where Izzo felt comfortable with him starting on Theo Pinson, though the six-foot-six wing never really challenged Jackson by isolating against him or forcing him to negotiate a screen in the pick-and-roll.
Three-pointers have accounted for 39.4% of his shots, as he’s averaged five such shots per 40 minutes. Michigan State puts him in the pick-and-pop a couple of times per game and there have also been plenty of instances for Jackson to space out to the three-point line on possessions that get deep into the shot clock.
He is mostly an open-shot shooter at this point of his development, doing a lot better when he has the chance to set his feet and go through his mechanics without being rushed than when he’s forced to relocate after setting a pick or pull the trigger quickly against a closeout – nailing just eight of his 28 three-point attempts so far, with three of these makes coming in the game against Duke alone.
Opponents have closed out to him with some urgency, though, which has opened up the dribble drive off the shot fake a decent amount. Jackson is well coordinated and can take it from the top of the key to the rim on a couple of dribbles but struggles to maintain his balance through contact and has the ball stripped away from him in traffic quite a bit – turning it over on 18.5% of his possessions.
He also has yet to show much of a stop-and-pop jumper or side-to-side shake and his handle is only rudimentary. When he puts the ball on the floor, Jackson can only go on a straight line drive as now, which often ends up with him trying to finish in a crowd, though he’s shown some flashes of being able to make a kickout pass to the strong-side against a collapsing defense here and there.
His touch on non-dunk finishes is only average and he can’t finish through contact yet - converting an unimpressive 58.4% of his 29 shots at the rim so far .
Jackson figures to be someone who could play above the rim as a target for lobs diving to the basket off the pick-and-roll or spotting up in the dunker’s spot but that has rarely been asked of him at Michigan State, with only six of his 17 makes at the rim assisted.
He gets the ball some with his back to the basket on emergency post-ups late in the shot clock and when the opponent switches on down screens. Jackson can get a lefty turnaround hook with decent touch out on these instances but is yet to show some semblance of a diverse post game, in terms of power moves or working his man with shot fakes, and his feel for recognizing double teams is only so-so.
He is asked to help facilitate Michigan State's offense from the elbows quite a bit, doing well on pre-arranged reads but not yet showing himself to be a particularly special passer – assisting on just 8.5% of the team's buckets when he’s been on the floor so far.
His most impressive contribution on offense so far has been crashing the glass. Jackson gets after it, has a seven-foot-four wingspan to rebound outside his area and a quick second jump to fight for tip-ins or 50-50 balls, also involving himself in enough scrums to get some second chances via the whistle – collecting 11% of Michigan State’s misses when he’s been on the floor and earning eight foul shots per 40 minutes this season.