Isaiah Thomas Wants to Be a Starter… Should He Be?

With the Celtics heading into their critical stretch run, much of the team’s success has been attributed to point guard Isaiah Thomas. Thomas has met and surpassed the expectations of many after being acquired by Danny Ainge at the deadline in a deal that is widely considered to be a heist. He has instantly become a fan favorite and so far has squashed any reputation he previously had of being a bad teammate. Any questions about how Thomas’ arrival affects the development of rookie Marcus Smart have been pushed to the side as the Celtics gear up to make their unexpected playoff run.

Isaiah Thomas had arguably his best game as a Celtic last time out against Detroit, scoring 34 points in 30 minutes on just 17 shots while finishing the game with a remarkable +35. He has excelled in a bench, sixth-man type role with Boston, perfectly filling many of the Celtics needs on the offensive end. With Thomas playing so well and Boston’s most important stretch of the season beginning tonight in Cleveland, moving the scoring guard into a starting lineup that has struggled is not out of the question.

Thomas, who is under contract through 2018, has already expressed the desire to start on more than one occasion.  As the new guy coming over in a trade, Thomas has shown he’s willing to do whatever Brad Stevens asks, but as we move forward, will Thomas be satisfied to come the bench?

The more important question for the Celtics to answer is: what is Isaiah Thomas’ role on this team moving forward? Is he a starting NBA point guard, and, therefore, the Celtics point guard of the future? Or better used as a scoring guard off the bench? Is Thomas’ impact on the team as profound as the eye test says it is?

For Boston, figuring out exactly what the team has in Isaiah Thomas allows them to better assess needs moving forward. Here’s a detailed look at Thomas’ impact, and what it means for where he fits on the Celtics now and moving forward.

Offense

Isaiah Thomas is an offensive wizard who has gone from a bad situation in Phoenix  to Boston where he is a perfect fit. The Celtics have given Thomas the reigns of the offense when he’s on the floor, allowing him to run a high screen with one of Boston’s bigs with the rest of the Cs playing off Thomas’ penetration.

Thomas ranks in the 93^rd percentile in the NBA as a pick and roll ball handler, according to NBA.com, a rank that is unrivaled by anyone else on the Celtics roster. Kevin O’Connor from CelticsBlog aptly covered how Thomas’ pick and roll ability would greatly benefit the Celtics offense following the trade, and he has undoubtedly been proven correct. The pick and roll is such a critical play in today’s NBA game, and even more critical in an offense predicated on pace and space. As Kevin notes, Thomas gives the Celtics the elite pick and roll scorer the team desperately needed.

A part of Thomas’ offensive game that is recognized, yet understated, is his ability to get to the free throw line. Free throws don’t receive the same hype among the analytics crowd that 3-pointers do, and fans view a player, like James Harden, who excels at getting to the free throw line as boring. However, for even an average free throw shooter (which Thomas is not) a possession ending in free throws, as opposed to a 2-point shot or 3-point shot, is the most efficient type of possession in basketball. As an example, look at Isaiah Thomas, whose shooting splits with the Celtics are 42%/34%/86%. This means that the expected value of a Celtics possession ending in a Thomas 2-point shot is .84 points. For a 3-point shot, it’s 1.02 points. For a Celtics possession ending in a pair of IT free throws, the expected value is 1.72 points.

That is a massive difference. Even though Thomas’ shooting numbers are modest at best, his ability to get to the line so often makes him an efficient player. Thomas ranks in the top 5 of NBA point guards in true shooting percentage, a statistic that takes into account 2-point field goals, 3-point field goals, and free throws. His efficiency is especially impressive given his 32.0% usage rate. Among the top 5 point guards in usage rate, only one ranks higher than Isaiah Thomas in true shooting percentage, and there’s no shame in losing out to the best shooter in the world.

The reason free throws don’t dominate analytics, as addressed here, is because a player cannot get to the free throw line whenever he wants and the differences in team free throw percentages vary much less than the differences in 3-point percentage. But for a guy like Isaiah Thomas, whose free throw rate with the Celtics (.492) is nearly on James Harden level (.559), it feels like he can get to the line whenever he wants.

Many of the league’s better teams have unimpressive free throw rates, but those teams make up for their lack of free throws by knocking down (3-point) shots. For a team like Boston that struggles from behind the arc, a few more possessions per game that end in two free throws is huge, and has often proven to be the difference between games the team lost earlier in the year and games they have been able to win since the all-star break.

Isaiah Thomas’ offensive rating with the Celtics is 108.8, easily the best number on the team. As shown above, that rating is fueled by Thomas’ pick and roll savvy and ability to get to the free throw line. But does that mean he should start?

Defense

It’s no secret that Isaiah Thomas struggles on the defensive end. The important question to answer is the following: To what extent does Thomas’ defense diminish what he does on the offensive end? The answer to that question shows Thomas’ true impact on the floor, and how he stacks up with starting point guards in the NBA.

Isaiah Thomas simply does not stack up defensively compared to other point guards around the league, and no statistic highlights that more than ESPN’s Defensive Real Plus Minus statistic (DRPM), where Thomas ranks 81^st out of 83 point guards listed with a -3.66 DRPM rating. While RPM is not perfect, it does typically correspond with the general eye test, and when taken along with other evidence, can be useful in measuring a player’s impact.

The Celtics defensive rating with Thomas on the floor (105.3) is not good, ranking second worst on the team only to James Young. Thomas primarily struggles against the NBA’s bigger, stronger guards one on one. Since he has come to Boston, opposing teams have tried to target him on the defensive end, a strategy that has largely been successful. Here are some of Thomas’ defensive stats with the Celtics in defending certain play types:

It is important to note that those numbers are taken from a small sample size of games, and there is some indication, based on his numbers with Phoenix, that Thomas’ defense is better than those numbers suggest. However, there is also indication that defenses are targeting Thomas more now that he is in Boston. For example, teams are isolating Thomas 14.8% of the time in Boston, compared to 9.9% of the time in Phoenix.

Like many other players, Thomas’ defense also takes a hit the more he is used on the offensive end. In the 4^th quarter of games when Thomas’ usage rate jumps to 36.7%, his defensive rating also increases to 115.0. This is not of great concern to the Celtics late in games, as Thomas has a ridiculous 117.4 offensive rating in 4^th quarters while in Boston, but it does provide some indication that if the Cs require him to carry the offensive load, especially against team’s starting units, Thomas’ defense will suffer.

Should Thomas Start?

While Thomas’ exceptional offensive game gets most of the attention, his defense diminishes some of his overall impact. ESPN’s real plus minus stat has Thomas as the 28^th ranked point guard overall, significantly behind Marcus Smart, who ranks 14^th. However, that should be taken within context. For this year’s Celtics team specifically, there is no doubt that Thomas is the more valuable player. The Celtics simply have no other player capable of doing the things Thomas does on offense. Right now, it is easy to overlook Thomas’ defense because the Celtics need his scoring so badly, and because his offense outweighs his defense, the Celtics are much better off with IT on the court.

Moving forward, however, as the Celtics continue to add more capable offensive players, which they will need to do in order to contend in the coming years, Thomas’ impact will not be quite as profound. His profile better fits the role of bench scorer, rather than starting point guard, where the Cs would rather have a guy who can defend the league’s top point guards from the tip.

This is not a knock on Thomas. As we have seen this year, his impact off the Celtics bench is more than substantial. Doc Rivers talks about guys being stars within their roles. Isaiah Thomas can be, and perhaps already is, the MVP of 6^th men. Let Marcus Smart and Avery Bradley set the tone on the defensive end to start the game, and then bring IT off the bench to kill the opposing team’s second unit, where he can better matchup defensively.

Whether or not Thomas will be satisfied with that role long term is another question. If the Celtics are successful with Thomas in that role, the way they have been of late, Thomas will not complain. But if the Celtics, particularly the starting lineup, struggle, Thomas will undoubtedly feel he should start and will likely speak his mind. That’s how the NBA works.

For what the team is paying Thomas, the Celtics are getting more than their money’s worth with IT succeeding in that role the way he currently is. While Thomas may not be the Celtics top star for years and years to come the way he is now, he will be a star in the 6^th man role, and the Celtics can rest assured that they have added a crucial piece to the puzzle on their quest for banner 18.