A big reason the Boston Celtics are home for the summer is they had no other reliable scorers outside of Isaiah Thomas. (Maddie Meyer/Getty Images)

There is a reason the NBA Playoffs are far more predictable than the other American professional sports leagues. In baseball, a couple of pitchers can steal a series. In football, anything is possible in a one-game situation. In hockey, a hot goalie can change everything.

But in basketball, an old axiom tends to ring true: The team with the most talent wins the series.

That was something the Boston Celtics entered their first round series with the Atlanta Hawks needing to overcome. The Celtics are an undeniably fun team to watch: they play hard, are led by players with fun personalities like Isaiah Thomas and Jae Crowder and are well-coached by Brad Stevens.

In the crucible of a seven-game playoff series, though, the thing that usually winds up being the difference is pure talent. And when you lined up Boston against its first round opponent, the Atlanta Hawks, there was no comparison. It took the Hawks some time to finally begin to use that talent disparity to their advantage. But once Atlanta did after losing Games 3 and 4 in Boston, they cruised to comfortable victories in the final two games of the series.

Thursday night saw Boston’s season end, as Atlanta cruised to a 104-92 win that eliminated the Celtics in six games. Despite the season-ending loss, it was a step in the right direction for Boston. The Celtics improved on their playoff performance from last season, when they were swept by the Cleveland Cavaliers, and they also improved from 40 wins to 48.

But as Stevens said after Thursday’s game, Boston has plenty of work to do if it wants to go from being a team that is tough to deal with in the regular season but a quick out in the playoffs to one that has a chance to be a true contender.

“People have told me all along there are two really tough tasks,” Stevens told reporters during his postgame news conference. “One is being a really competitive team, a top 10 to 15 team on offense and defense, to be in the conversation.

[But] the next one is tough. We’re learning a lot. We learned a lot in this playoff series, and one thing I learned in this series is we have to get a lot better, and that starts with me.

“We’ll all be better the next time we step on the court.”

Stevens has a lot less work to do in that department than General Manager Danny Ainge, who is likely to have a busy summer ahead of him. If this series proved anything, it is that Stevens is getting just about everything he possibly can out of the roster at his disposal.

Boston’s All-Star, Isaiah Thomas, is a good player who has been placed in the absolute perfect scenario by Stevens: a ball-dominant guard who can control the ball at will on a team with few, if any, other legitimate scoring options. The Celtics surrounded him with lots of excellent defensive players, from Avery Bradley and Crowder to Marcus Smart and Amir Johnson, but also have little-to-no shooting to speak of in a league that relies more and more on shooting to space the floor.

The Celtics were usually a giant puzzle, one with ill-fitting pieces that Stevens had to try to cobble together into a working roster. And, for the most part, he did.

But it’s hard to gloss over a lack of talent in the playoffs. And this series – particularly once Bradley was lost with a hamstring injury in the fourth quarter of Game 1 – was proof that Boston simply lacks talent. Hawks big men Paul Millsap and Al Horford are both demonstrably better than anyone on the Celtics, while Jeff Teague and Thomas are on a similar level.

There’s a reason why Boston’s two wins, which both came at home, also came with Thomas having gigantic performances: For the Celtics to win, they needed Thomas to have a huge game. Otherwise they simply lacked the offensive firepower to keep up.

Ainge’s charge this summer will be to begin upgrading that talent to give the Celtics a chance to advance in the East. That’s not to say Ainge hasn’t been trying – all of the picks he acquired from the Brooklyn Nets in the trade that sent Paul Pierce and Kevin Garnett away in 2013 have been burning a hole in his pocket for some time.

Boston will have three first-round picks – including Brooklyn’s pick, which is basically a lock to be in the top five – and could have more than $50 million in cap space to try and upgrade the roster; Ainge will undoubtedly swing at every big fish that’s out there. Every top free agent will be pursued – beginning with Kevin Durant – and if stars like Sacramento Kings center DeMarcus Cousins or Chicago Bulls guard Jimmy Butler shake free, the Celtics will be involved in discussions for any of them.

How successful Ainge is this summer will determine just how high Boston’s ceiling is next season. The past two years the Celtics have made strides, but this team is what it is: a fun, hard-working bunch that isn’t good enough to make it out of the first round even in the Eastern Conference.

If that’s going to change, it’ll be up to Ainge to use the assets he’s been stockpiling the past few summers to do so.