Per Yahoo! Sports and Adrian Wojnarowski, unrestricted free agent Amir Johnson and the Boston Celtics agreed to a two-year, $24 million deal. Johnson is one of the top free agent forwards on the market at age 27, serving Toronto (and previously the Detroit Pistons) as their starting power forward.

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Athletic, long and defensive-minded, Johnson averaged 9.3 points and 6.1 rebounds per game in 75 games for the Raptors last season. The Celtics fill a need, desperately needing frontcourt defense outside Tyler Zeller.

Amir Johnson brings all that and more. Unfortunately, the $12 million/year price is steep and probably an overpay. However, according to Steve Bulpett of The Boston Herald, the second year of Johnson’s contract is non-guaranteed. Not only does this detail make the deal look significantly better, it also could serve as an excellent trade chip, should the Celtics and GM Danny Ainge look to make a big splash in the trade market.

Still, operating under the assumption that Johnson will suit up for Boston this season, the Celtics have definitely improved upon their most glaring weakness: rim protection.

While he is far from an elite rim protector, Amir Johnson is quantifiably better than Jared Sullinger, Brandon Bass and Kelly Olynyk. Those three contested a paltry number of shots at the rim (33, 19 and 33-percent, respectively) last season, while all allowing well over 53-percent shooting around the rim, per Nylon Calculus.

Johnson, on the other hand, gave up a slightly lower conversion rate of 52 percent but on a much greater percentage of contests, 38. While he does not possess top-tier rim protection skills, he is relentless and uses his athleticism to hover around the rim, making life difficult for slashers.

When paired with Tyler Zeller, who contested an impressive 55 percent of shots and gave up just under 52 percent, the two will make a solid, above-average rim protecting duo.

Furthermore, Johnson is a rare model of durability and athleticism down low, having played in 85-percent of games each of the last six seasons.

Sullinger and Bass, while expected to remain on the roster, will probably see reduced playing time in favor of a more defensive-minded approach. Stevens’ schemes have already helped guide — outside of Isiah Thomas — an otherwise below-average group of offensive talent to the 13th best scoring offense in the NBA last season, 101.4 points per game.

Now, with a rim-protecting, hard-nosed, scrappy athlete in Amir Johnson, Stevens can look to implement the defensive schemes that made his Butler teams so potent. Moreover, guards Marcus Smart and Avery Bradley can now take more risks on the perimeter with the knowledge that a capable defensive frontcourt can shore up any empty gambles — not to mention that first-round pick Terry Rozier will have the same luxury as he adjusts to playing NBA-level defense.

Even on the other end of the court, this is an excellent move. Take a look at Johnson’s shot chart last season:

Not only are the Celtics getting a great athlete on what is effectively a bargain of a contract, they’re getting a smart player, someone who doesn’t try to do too much and is above-average at what he does do. That’s efficient basketball, and it will likely pay off for Boston, especially given a reduction in minutes for Jared Sullinger.

While Sullinger came through for the Celtics in spots last season, he too frequently stepped out to the three point line and was an abysmal 28-percent on shots that accounted for 26-percent of his total field goal attempts. And I’ve already gone over what a liability Sullinger was around the rim.

Although he provides great energy and can occasionally catch fire, Sullinger is now expendable and may find himself part of a bigger move. Danny Ainge has gained fame (or infamy) for orchestrating blockbuster deals. Given the logjam of guards on this team, something has to give, and it may even be shipping Johnson off mid-season when contending teams are desperate to fill needs.

Regardless, even if Johnson doesn’t produce to the level last season’s numbers say he should, Boston really loses nothing. They’re already a playoff team, finishing 24-12 after trading away Rajon Rondo and Jeff Green, a mark that extrapolates to a 55-win season.

And they’ve just made what should be one of the most underrated moves of free agency.

Any time a team can acquire a player to immediately strengthen their biggest weakness while keeping said player as a valuable trade asset, it’s a huge win — perhaps the first of many for the Celtics this offseason.