This has been the absolute season from hell for the Boston Celtics. They've been dealt with a myriad of injuries and health complications all throughout the season, both COVID-19 related or otherwise.

Kemba Walker started off the year on the shelf, missing the team's first 11 games. Walker would end up missing 27 total out of the team's 70 games played. Marcus Smart has missed 22 games for the team as well.

Trade deadline addition Evan Fournier just started finding his shot with Boston when he got hit with COVID-19. In his words, it felt quite literal, as the Frenchman admitted to feeling concussed by the illness thereafter:

“I've been feeling really weird, to be honest,” the Celtics addition said, via USA Today. “My plan was to stop talking about it so it might help me, but the thing is it's like I have a concussion. Right now, it's actually doing a little bit better, but at first, the bright lights were bothering my eyes and my vision was blurry.

But at the end of the day, the team is built around its two cornerstones: All-Stars Jayson Tatum and Jaylen Brown. The Celtics actually started off the season hot, posting seven wins in their first 10 contests with both Tatum and Brown absolutely rolling.

When Jayson Tatum fell ill with COVID-19, things took a turn for the worse, with the Celtics never really recovering, and apparently neither did he. Despite a couple of minor win streaks that felt like they might be figuring it out (Fact check: they didn't), the Celtics hovered around mediocrity throughout the rest of the season. They stand at 35-35 through 70 games, a fitting ode to a season where they didn't really achieve much.

While the Celtics' Tatum and Brown are surefire stars for years to come, franchise cornerstone stability has been fleeting in the NBA, as we've seen in the last few offseasons. That's why the Celtics cannot rest on their laurels, trying to run it back with the same roster iterations over and over until Tatum and Brown get fed up. The Celtics must trade Marcus Smart.

Trade Marcus Smart: The Huge Decline

Marcus Smart Celtics team meeting

While there are many factors that contributed to the Celtics' lost season, arguably the biggest has been Marcus Smart. Celtics fans have had the longest love-hate relationship with Smart for years. He's come up with some of the gutsiest plays throughout the team's recent string of NBA playoff successes. He's served as defensive agitator against opposing stars big or small and vocal leader when the team needs some fire to rally around.

Smart has been an integral part of the Celtics' identity for years. But the difference this year is that Marcus Smart is gone.

Marcus Smart has always been an inefficient scorer. He's only shot above 40% from the field once in his entire seven-year NBA career. After improving his outside shot during the previous two seasons, he's fallen back to an ugly 33% on nearly five attempts per contest.

But the reason Smart has been worth playing was always because of his defense and intangibles. During the past three seasons, the Celtics hung their hat on the defensive end. Last year, they ranked fourth in defensive rating in the entire NBA. The previous two years, the Celtics sixth and second in the NBA on the defensive side of the floor.

Smart has always led the charge in that department. But his defense has seemingly fallen off a cliff.

His individual defensive rating numbers during those three years prior were absolutely stellar. His personal impact rated to 99.6 in 2018, 106.7 in 2019, and 104.6 in 2020. All those marks were well below the average line of scoring for opposing teams those seasons.

But this year, the Celtics have gone from a top 6 defense to a below-average one ranking at 18th in the NBA. Marcus Smart's pedestrian defensive effort this season is a big reason why, with a defensive rating of just 111.3 which is basically league average.

So if Smart is playing as just a league-average defender, there's absolutely no reason to put up with his crazy inefficient production on offense. This especially because both Tatum and Brown have no problem putting the ball in the basket.

While some would argue that Kemba Walker has been equally underwhelming this season, it would be virtually impossible to trade Walker given his contract. Marcus Smart's deal is expiring after next season and is relatively palatable at under $15 million for a team willing to gamble on the veteran.

How trading Smart impacts Celtics

Bradley Beal, Wizards, Jayson Tatum, Celtics

Yes, you could hope his defense improves again next season. But with only just so few shots to contend with star players nowadays, it would serve Danny Ainge and the Celtics' best interest to move Marcus Smart while he still has trade value.

But at the same time, getting rid of smart also allows their stars to learn how to play on the ball more.

Think of Jayson Tatum's childhood friend and mentor Bradley Beal. The Washington Wizards star used to be known as the shooting guard playing off of ball-dominant John Wall. But with Wall being sidelined with injuries for two consecutive seasons, Beal had to learn how to be the alpha, and boy has that helped his game develop.

Bradley Beal has turned into a bona fide superstar. And while Jayson Tatum and Jaylen Brown are already hovering around that level, with Tatum arguably already exceeding Beal depending on how bullish you are on him, the potential improvements they can make still ring true.

Beal's assist numbers slowly crept up until his supernova season last year, averaging 30.5 points with a career-high 6.1 assists per game. While Tatum and Brown already generate 4.3 and 3.4 assists per game respectively, neither of them are considered elite playmakers for others just yet.

Marcus Smart actually leads the team in assists, often acting as a ball-dominant guard alongside the two star swingmen. But with his inability to space the floor well and just so-so passing ability, he's definitely not the guy you need to unlock Tatum and Brown's next gear.

At least with Kemba Walker, he shoots at a respectable rate from deep. If Tatum or Brown dish off for a Marcus Smart three instead of creating something themselves, the other team will live by that result.

Trading Marcus Smart could be addition by subtraction, and be the subtle change that impacts the Celtics in a big way.