Avid fans of college basketball will note a couple of differences between the rosters of the teams in major conferences and those from the mid-majors. Not the more obvious differences in talent level, size and athleticism, but in terms of depth and guard rotation.

So often as to be normal, mid-major teams will run with three- or four-guard line-ups, and sometimes doing so surrounding a ‘big’ man who stands about 6’8. More often than not, at least one of those guards will have no discernible impact in the stats column. They will finish with season average of 24 minutes, 4 points, 2 rebounds and 2 assists per game. They may or may not be able to shoot open threes. They play big minutes anyway because the coach seems some value in them.

This is supposed to be done in order to mask deficiencies, in terms of talent yet specifically in frontcourt talent. Capable big guys are hard to come from, even at the mid-major level, as are capable lanky forwards. Talent is funnelled upwards, and anyone with any pro potential tends to be picked up by those near the top. With some exceptions – Sam Houston State, Northwestern State – the four-guard line-ups are a product of circumstance rather than design. Mid-major teams generally having a quality big man is rare, let alone two with a strong wing as well. Lower ranked teams do this because they have to, not because they choose to.

It is extremely rare, then, to see the concept in effect at the NBA level. Yet in Terry Rozier, the Boston Celtics essentially have exactly that – a free-roaming extra guard.

The difference is that the Celtics are choosing to, because this one is an absolute freight train.

Rozier is not the traditional overlooked talent. He played two years at Louisville back during the peak of Rick Pitino’s relevance, an obvious NBA player since the day he joined the Cardinals, before being drafted by the Celtics with the 16th overall pick back in 2015. And although he did not play a huge amount in his first two NBA seasons – the first one especially – Rozier still made some headlines due to the fact that Celtics general manager and Vice President of Basketball Operations Danny Ainge was said so vehemently to be such a fan of his.

It was reported that Rozier was requested by the Orlando Magic as a part of a trade package sought for Serge Ibaka, who Boston were said to be interested in. At this time, Rozier was playing only 19 minutes per game, and not playing them especially well, an off-ball guard who struggled to make shots and whose defence was undermined by these limitations. But Ainge stuck with him, partly perhaps as a reflection of the declining returns he saw in Ibaka (fairly, as it turns out), but also an endorsement of Rozier himself.

In the midst of his break-out this season, Rozier has begun to reward him for that.

Rozier has done this by playing a versatile, adept and hustling game, combining speed with developing skills. Notwithstanding the above introduction, Rozier should not be confused for being unproductive. He is very much not the 24mpg/4ppg/2pg/2apg player from the Generic State University Placeholders, who Coach Somebody raves about purely for his intangibles and his 'coach on the floor' nature, ignoring that the guy cannot dribble or shoot. Rozier is instead a talent, if a unique and short one.

Most obviously, Rozier is an NBA calibre athlete. This is perhaps best evident in his rebounding.

Despite playing only 24.5 minutes per game, Rozier grabs 4.5 rebounds in that time, a good mark for a wing player but an excellent one for a 6’2 de facto point guard. In particular, Rozier crashes the defensive glass to ignite the break, an area in which his straight-line speed can really come into play.

That same speed and crash can be found in his willingness ability to play the passing lanes, which in recent times even won the Celtics a game.

For whatever reason, despite this athleticism, Rozier is a poor finisher at the rim when not dunking. He misses and has always missed a lot of lay-ups, shooting a lowly 47.4% at the rim and up to only 50.4% this year, both distinctly below-average marks.

What made this worse historically was a very streaky three-point stroke, a very poor 22.2% outside shot maker as a rookie and a still-poor 31.8% mark as a sophomore. That is OK from a stretch five big learning the craft, but not a guard, and while Rozier’s style of play and shot selection are right to largely eschew the mid-range two-point shot in favour of the threes and the layups, it only works if he is good at them.

In one of these two areas, though, Rozier has turned it around. The rookie-to-sophomore three-point improvement has been followed up by a sophomore-to-young veteran one. Rozier now shoots a healthy 37.6% from outside on 4.5 attempts per game, going from poor shooter to good shooter in a year and a half having made the adjustment to the longer-range three and big league defenders.

With this comes a renewed purpose on the court. And with that in turn comes a bigger role on the team.

Kyrie Irving, of course, has the starting point guard position locked in, and despite his own failings (similar if stylistically different to Rozier’s), Marcus Smart is the first guard off the bench and a decent quality point guard of his own. To get into the game at all as the third point guard on the depth chart, then, Rozier would have to earn the spot in some other way.

Therein lies his value. As the free safety, Rozier is out there to harass opposing players. He can handle the ball a little bit, as he proved at Louisville, but largely doesn't, letting Irving do the bulk of that work (or splitting the role with Smart when they pair up) and instead going to the glass, playing the passing lanes, spotting up and running the court. In the half-court, Rozier's decision-making and ability to exploit small spaces has improved, and although he still all too often misses the layups, his speed, agility and knowledge of how to use them are all weapons to which the Celtics can turn.

Even without Gordon Hayward, the Celtics have quality wings. Jaylen Brown and Jayson Tatum are a striking young duo on the wings – see also today our profile on Tatum’s role in replacing what Hayward was supposed to offer - while Smart provides cover there, and Semi Ojeleye gets a few solid minutes as a defensive specialist in need of more experience. Yet it is significant that Rozier's play as essentially a tiny two-guard adds further flexibility to their team. It is surely not for nothing that two of the three most productive five-man line-ups Rozier has featured in this year have been three-guard ones.

If he is aggressive on defence, attacking in looking to drive the ball, spotting up well and crashing the glass whenever he can, then Rozier is a threat on any play. He may not have the skills nor all that much opportunity to show what he can do as a full-time half-court point guard - yet - but as a free safety type of bench guard, Rozier is already a handful. 

The beauty of the irregular line-ups he plays in, and of his irregular role within them, is that if opposing teams do not switch down to match, then Rozier has an exploitable matchup on the offensive end. Terry Rozier can do a much better job defending the Jeff Green, Ersan Ilyasova and Marvin Williams types than those types can do when defending Terry Rozier. And now, he understands that as well.

It is often said that the Celtics and Brad Stevens yearn for position-less basketball. Rozier’s free-natured, positionless-play is perhaps the perfect embodiment of that. The -26 net rating of his youth and -8 of last year is now a +7. Rozier has grown leaps and bounds, and in a unique way that is becoming hard to guard, however well known it is amongst advanced scouts.

The casual fan may not have heard of him before, and that’s all right. But if he makes important plays in Thursday’s game, don’t say you weren’t given the heads up.