This 76ers-Celtics series very well may be the real NBA Finals

Three teams finished the regular season with 54 or more wins. Thanks to the implosion of the Milwaukee Bucks, only two remain. Three teams finished the regular season in the top-10 in both offensive and defensive efficiency. Thanks to the floundering performance from the Cleveland Cavaliers, only two remain. 

Monday night, those two teams — the Boston Celtics and Philadelphia 76ers — will face off in Game 1 of a best-of-seven series. And while we're only in the second round of the playoffs, a strong case can be made that this series might as well be the NBA Finals. With the Bucks now watching at home, the winner of Celtics-Sixers will certainly emerge as the favorite to come out of the East, and will probably be deemed the team to beat going forward. 

There are so many reasons to be excited for this matchup. For one, there's all the history. This will be the 22nd time the Celtics and Sixers face off in a playoff series, the most between any two teams in NBA postseason history, and their third time meeting in the playoffs in the past six seasons.

There's also stakes. The Sixers haven't advanced past the second round since 2001 — what happens if they fail to do so again? Will Doc Rivers be in trouble? Will James Harden bolt for Houston? Will Joel Embiid start itching for an exit? 

The Celtics have seemingly been on the precipice of a title since Jayson Tatum and Jaylen Brown came on board, but what happens if they squander another chance? Will coach Joe Mazzulla receive the blame? Will Brown make good on his semi-regular quasi-threats to leave? Will the team's ownership, which is spending more in luxury tax payments this season than it has in the previous nine combined, cut costs?

This series should be an absolute blast. Here are the stories, trends and matchups that will determine the winner.

Joel Embiid's health

We'll start with the most obvious one. Embiid's status for the start of this series is still in question — he is "doubtful" for Game 1. He suffered an LCL sprain in his right knee in Game 3 against the Brooklyn Nets and sat out Game 4. The Atlanta Hawks pushing the Celtics to six games in the first round helped the Sixers, but a quick return is not a sure thing.

Without him, the Sixers will likely turn to third-year center Paul Reed. Reed was solid against the Nets — 7.3 points and 7.0 rebounds in 16.5 minutes per game — but these Celtics are in a different stratosphere. They'll go at Reed every time down the floor and make him guard in space. It's hard to envision the Sixers winning even a single game without Embiid.

There's also the question of how he looks and feels if/when he does return. During the regular season, Embiid torched the Celtics. He averaged an absurd 36.8 points per game in four matchups against the Celtics and shot an even more absurd 61.2% from the field. Oh, he also added in 11.8 rebounds, 4.3 assists and 1.8 blocks per game. And let's not forget his 52-point explosion in an April win. 

The point being: The Celtics might have more depth and talent, but, if healthy, Embiid would be the best player on the court. He has the ability to carry the Sixers past the Celtics by himself. The question is whether his knee will allow it. 

Joe Mazzulla on the big stage

This is a big series for Mazzulla. He did a great job after taking over for Ime Udoka, but he's looked overmatched at times. His end-of-game play calls have become predictable. His rotations have been strange, particularly his aversion to closing games with Derrick White, the team's third-best player this year. He didn't double Trae Young down the stretch of Game 5, allowing him to go off and the Hawks to steal a win. 

In a way, the fact that the Celtics have so much depth and talent makes his life harder. He actually has choices to make. He can't just roll out the same five guys every game in crunch time. 

For example, Tatum and Brown are always going to be on the floor, but he has two strong front-court options in Al Horford and Robert Williams III — does he go with just one of them or both? And if it's just one, then who does he choose? And how does he decide between the trifecta of Marcus Smart, White and Malcolm Brogdon, the Sixth Man of the Year? He's almost always gone with Smart, but you can make the case that's a mistake. And what about Grant Williams, who was buried against the Hawks? He might be a good option to slot onto Embiid for a few minutes. 

All that said, his players clearly like him, and the results have mostly been there. But against the Sixers, Mazzulla's decision-making is going to be under the spotlight more than ever. 

James Harden's 3-point shooting

Do you know what Harden shot from inside the paint against the Nets? Seven-for-30. Do you know how many free throws he took in four games against the Nets? Eleven. 

None of that is going to cut it against the Celtics, where the margin for error is basically nonexistent. Also, the Celtics are loaded with big, strong, athletic wings who should be able to hang with Harden, never mind Williams, one of the game's premier rim-protectors, lurking on the backline. 

Maybe Harden finds a way to bully his way into the paint and get to the foul line, but it's unlikely. The thing is, the Sixers are going to need Harden's scoring, for obvious reasons but also because historically Tyrese Maxey has struggled facing this Celtics group (8.2 points per game on 34% shooting in 10 games). That could very well mean the series comes down to whether Harden can catch fire from deep. 

Al Horford guarding in space

The only reason the Sixers defense works is that Embiid is always lurking in the back, deterring drivers and protecting the paint. Without that, there's no way for a team trotting out a backcourt of Harden (uninterested) and Maxey (undersized) to stop opponents, let alone at a top-10 rate. 

But if Embiid has to worry about his man draining shots from deep, well, the whole thing falls apart. This is why Horford has given the Sixers fits over the years. He's been one of the few players who could hang with Embiid on defense while dragging him out to the 3-point line on the other end. 

The problem is, at the age of 36, Horford is not looking so spry. The Hawks attacked him over and over in pick and rolls, and the Sixers will likely do the same. He's still a knockdown shooter (44.6% 3-point shooting on 5.6 attempts per game during the regular season), but if he can't hold his own on defense, the Celtics will have to rely more on Williams, a better defender than Horford but not a floor-spacer. 

Prediction: Celtics in 6

The Sixers can win this series. But Harden's lack of burst means they're going to need an all-time series from Embiid, which is hard to imagine him having with an injured knee. The Celtics are the deepest, most talented, and most versatile team remaining in the playoffs. The prediction here is that they take care of business and cruise to the finals.

Yaron Weitzman is an NBA writer for FOX Sports and the author of Tanking to the Top: The Philadelphia 76ers and the Most Audacious Process in the History of Professional Sports. Follow him on Twitter @YaronWeitzman.