The Boston Celtics have defied every bit of expectations this season.

A year in which Gordon Hayward and Kyrie Irving were preparing to immerse themselves in Boston quickly saw the plan put on hold after the gruesome injury to the small forward. No matter, Irving has played as well as ever, pairing with Al Horford to put together All-NBA cases. The youngsters—Jaylen Brown and Jayson Tatum, primarily—have fans drooling for the future and pundits accelerating the championship timelines of the organization. And that’s before factoring in Aron Baynes brawling on the inside, Marcus Morris adding to the versatility, and Marcus Smart providing positive impact on the floor, which always draws perplexed questioning.

What has gone under the radar is Terry Rozier. The man tossed into every possible trade scenario this side of the sun has remained the backup point guard with the team. Starting with one of the hundreds (exaggeration) of first-round picks, Rozier has steadied as a regular, with the basketball world dissenting about how good he really is.

Rumors always swirl around the Celtics, but those rumblings turned into gusts when the team’s high interest in trading up in the 2015 NBA draft for Justise Winslow was revealed. The reportedly rebuffed offer to the Charlotte Hornets included four first-round picks, one of which would have been an unprotected first from the Brooklyn Nets. Things didn’t work out that way, as the Hornets had their eyes set on bringing in Frank Kaminsky. The Celtics instead “reached” for Rozier at the 16th spot. Fans were bummed, and the media rolled its eyes as another pick seemed to be thrown down the rabbit hole instead of being used to grease deals.

Left Vegas last night, but 2 things I heard repeatedly: 1. Myles Turner will end up being steal of draft. 2. Terry Rozier was biggest reach. — Howard Beck (@HowardBeck) July 14, 2015

The first year, Rozier drew mixed reviews.

The crowded backcourt gave him limited opportunities, and he was rather inefficient when given some burn. His effective field-goal percentage scraped past 30, and he only played more than 15 minutes six times all season. But rookies aren’t all judged by these metrics. His development was seen through a different prism. Head coach Brad Stevens noticed the unique burst, and he was able to take advantage of playoff minutes when injuries whittled down the guard depth.

What has remained special about Rozier, even during that rookie season, was the rebounding. It wasn’t just an observed excellence; he provided statistical backing of his dominance. His total rebounding percentage was the highest of his career (10.8) during that first season in 2015-16. It hasn’t dipped below 10 percent for the rest of his young career.

In his sophomore year, the incremental improvements were evident. Across the board, he made major strides as he was allotted more playing time with the departure of Evan Turner—the de facto second-string ball-handler. He edged his way into more of a featured role, getting not only the chance to control the ball, but score when he had the opportunity. But making strides from abominable only gets you so far. His efficiency numbers still graded out as some of the worst among players with more than 400 shots from the field.

And this is where we’re at, getting to the point where we need more consistency from the 23-year-old. It reminds me of what my dad says when we play golf: “It only takes one shot to bring ya back.”

That’s the seesaw game of Rozier. You want 24 points on 8-of-11 shooting with six rebounds mixed in? Done. Two games later, you may get a three-point, one-assist night, followed up by a six-point, two-rebound performance. The output constantly shifts for a player whose efficiency levels are starting to sniff mediocrity, as his effective field-goal percentage now sits just a hair below the 50 percent mark.

Further improvement is essential to him being a reliable player moving forward, and that efficiency will have to come from three-point range, as his ability to finish at the rim leaves a lot to be desired. He has made a total of 98 shots at the basket throughout his career, which is less than the 141 Jrue Holiday has made in this season alone. The problem isn’t necessarily his ability to get shots off when he nears the bucket, so much as his finesse in getting them to drop.

For example, Rozier has taken a total of 216 shots at the rim in his career and has only knocked in 45.4 percent of them. Given those same opportunities, Kyrie Irving would have hit about 125 at his career efficiency around the basket. Using Irving isn’t exactly a fair exercise for Rozier, but it shows how far down the totem pole he is among guards in this aspect of the game. You can arguably call him one of the worst finishers at his position.

Taking contact when finishing at the rack may be his biggest issue. Above, you can see he gets bumped just a bit, and it completely alters the touch of his shot. It clanks off the front iron and misses rather badly. Most of the time, it seems that he misreads the proper angle to take off the glass and becomes afraid of the contact, or isn’t aggressive enough in pushing through it.

But if he’s going to get lambasted for that close-range efficiency, we also need to magnify his dominance as a rebounder.

His 16.0 defensive rebounding percentage ranks in the 95th percentile among combo guards, per Cleaning the Glass. That kind of figure is unexpected for a 6’2″ player, but his ball-hawking tendencies off missed jumpers allow him to be in the mix at all times. His Pterodactyl 6’8″ wingspan gives him that extra bit of oomph to sneak his hands past unsuspecting offensive rebounders.

Strong hands, aggression and effort are key components for good rebounders, and Rozier exhibits all those qualities in this play. Instead of lazily allowing a big man to corral the ball, he attacks the basket and hops into his man before leaping to snag the ball at its highest point. And a point guard getting the ball off a rebound is huge for transition opportunities.

This gives Stevens the versatility he craves. Rozier’s skill set gives him options to use in a variety of lineups, including when he wants to go extremely small with three guards. The team Boston is trying to become has this type of “switchability” across all positions, so having a backcourt member like Rozier who can fill in other holes at elite levels gives the coaching staff the option of playing him with different personnel. For instance, a Shane Larkin, Marcus Smart, Rozier, Tatum and Daniel Theis lineup has been the ninth most used five-man combination for Rozier this year.

Another aspect of Rozier’s game that flies under the radar is his ability to hold onto the ball. He is currently in the 100th percentile for combo guards with an 8 percent turnover rate. If he were to continue at this rate, he’d be one of only 30 other guards in NBA history to sustain that percentage. Add in the fact that a bulk of those guards were primarily catch-and-shoot options, and the figure looks even more staggering.

Of players who get 25 minutes of playing time or less, Rozier ranks 10th in touches with 46.1 per game. Every player in front of him has a turnover rate in double digits, and eight of them have a figure at 13 percent or higher. The ability to have and maintain possession so often is an underrated skill that often gets glossed over when analyzing his talents.

The free-flowing style of the Celtics limits the onus on the point guard to heavily create looks for their teammates, but it still takes self-consciousness to deliver that game plan. A good example is Shane Larkin: The 5’11″ spark plug never had a completed season in which his turnover percentage was lower than 15, but he has dropped that number below 10 percent this year.

Prospects flourish in this system time and time again because of the culture the team has created. There are no excuses for being young, and the high expectations have made them better. Still, draft analysts pick apart some of the players selected by the Celtics, and those players have often made them eat crow.

Rozier is just like those before him. He has jacked up his attempts from deep and is hitting treys at an all-time high of 37.2 percent. This forces defenders to actually close out on his shot, which didn’t seem like a strong possibility after his erratic shooting in his first two seasons. That, and the drastic improvements he has made in a litany of advanced metrics—PER, win shares per 48 minutes and VORP, for example—are important in distinguishing how far he has come.

For point guards, shot versatility is a great weapon to have in your back pocket. That capability helps stretch out defenders and gives an offense a bailout option in case a possession stalls. Being able to get off a shot takes some skill, but doing it at a reliable mark is what has separated Rozier from past years.

Having a player as dynamic as Rozier hit 34.7 of his catch-and-shoot looks would make a decent piece for any team. But when you can carry a second unit by draining 36.2 percent of your pull-up three-pointers, you can become a game-changer.

As a backup who plays significant minutes with Irving, his ability to hit standstill jumpers becomes a more lucrative feature. But just last year, we saw an Oklahoma City Thunder team implode when Russell Westbrook hit the bench. It’s nice to have other guards who can create for themselves a bit.

After looking at all these positives, it’s still hard to get past that big, fat 49.3 effective field-goal percentage. The mark has gradually increased over the years, like many of his measures, but the number still ranks in the bottom third at his position. This is part of the dilemma in fully evaluating him and answering the ultimate question of his overall merits.

The excellent Michael Pina of VICE Sports was able to bring some clarity, telling NBA Math, “He’s not efficient and is still a bit too hesitant with his shot selection, but has physical gifts that should eventually separate him from others who share the same role. I don’t think he’ll ever be a quality starter in the NBA, but in 20-25 minutes per game he can change games.”

Enthusiastically, he responded that yes, Rozier remains a positive. Pina also cited consistency as a weak spot for Rozier, which was just written about in perfect fashion by Ben Falk of Cleaning The Glass: “I don’t know how to measure it, but it’s always felt to me that the national coverage of young players is heavily influenced by which team they play for. Don a Lakers, Celtics, or Knicks jersey and you’re discussed differently, the spotlight shining a little brighter on your highlights, a little softer on your lowlights.”

NBA Twitter seems quick to jump on the games in which Rozier performs well, and a bit slower in outings where he fails to deliver. Catching glimpses of success is great for ceiling purposes, but seeing the missteps is just as important in properly analyzing players.

The book isn’t closed on Rozier, as his incremental improvement is likely to continue—pretty normal for a 23-year-old. Boston’s eventual championship push probably doesn’t hinge on him answering the question this year, but it certainly wouldn’t hurt to erase some of the doubters sooner rather than later.

As of now, things are looking hopeful, with the Celtics primed to take advantage of another acquisition.

Follow Thomas on Twitter @Trende19.

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Unless otherwise indicated, all stats are from NBA Math, Basketball Reference or NBA.com and current heading into games on January 18.