The Boston Celtics went into the Wells Fargo Center on Tuesday night as relatively heavy underdogs to a Philadelphia 76ers team that the national media has been raving about. The 76ers entered the season with a roster headlined by Joel Embiid and Ben Simmons, but back in November, they added Jimmy Butler. If that wasn't enough, they then went out and landed Tobias Harris ahead of the trade deadline.

The Celtics entered their matchup with the Sixers having suffered two straight devastating losses to the Los Angeles Lakers and Los Angeles Clippers, respectively, blowing an 18-point lead to the Lakers and following that up by coughing up a 28-point edge against the Clippers.

Not only that, but Boston was without Kyrie Irving and Aron Baynes, the latter of which being more significant than usual against an Embiid-led Philadelphia frontcourt.

Kevin Garnett, Celtics
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Most thought the 76ers would top the injury-riddled Celtics, but what ended up happening was far from what many expected.

The short-handed C's went into Philly and topped the 76ers by a score of 112-109, extending their dominance over a Sixers club that just can't seem to beat the Celtics.

It's blatantly obvious that Boston is in Philadelphia's head, as the Celtics took the season series last year 3-1 before ripping the 76ers a new one in a five-game playoff series. They then routed the Sixers on opening night and beat them on Christmas Day before heading into Philadelphia's backyard and beating them yet again on Tuesday.

Let's start with the simple facts: the Celtics are just flat out better than the 76ers. They are better offensively, they are better defensively, they are deeper, they are tougher and they are more well-coached.

Boston has an edge over Philadelphia in just about every single area, and the fact that Al Horford seems to own a whole lot of real estate in Embiid's head (to quote from Embiid himself in taking about Andre Drummond earlier in the year) just makes matters worse for the Sixers.

You know what else is clear as day? The Celtics do not like the 76ers. At all. The Toronto Raptors and Milwaukee Bucks may also be conference rivals, but they do not instill the kind of hatred in the hearts of Boston's players that Philadelphia does, and Embiid's big mouth may have a lot to do with it.

Jayson Tatum, Joel Embiid, Ben Simmons, Celtics, Sixers
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Embiid ran his mouth while the 76ers were down 3-0 to the Celtics in last year's playoffs. He ran his mouth during the offseason. He then ran his mouth yet again after the game on Tuesday, blaming the referees and saying that his 9-for-22 night had nothing to do with Horford and everything to do with him “sleepwalking” through the first three quarters.

Sure, Joel.

That brings us to another reason as to why Boston always beats Philadelphia: mentally, the Celtics are just stronger. They don't make excuses when they lose games, and they certainly don't put forth an immature persona through the media.

That matters late in games, where Boston has the intestinal fortitude to execute in big spots where Philly tends to fold.

You can blame 76ers head coach Brett Brown as much as you want, but at some point, Embiid, Simmons and Co. have to take some accountability and grow up.

Harsh words, but it's the truth.

I can't help but think back to a moment earlier in the season, when Embiid tried to get fancy with a windmill dunk and ended up missing it. Embiid and Simmons then laughed it off.

Danny Ainge, Kyrie Irving

That instance spoke volumes, as it tells us that the 76ers care more about style points than fundamentals. Remember: Simmons missed a crucial dunk during Game 3 of the playoff series against the Celtics last year in a similar fashion.

You can laud the Sixers' starting five as much as you want, but their complete lack of depth and their tendency to get rattled in close games is why they are multiple steps behind the Celtics in the Eastern Conference chase.

That's why they are also behind the Raptors, who are lead by a seasoned, battle-tested superstar in Kawhi Leonard, a player who has no heartbeat in big games and can rip you apart without even breaking a smile.

Plus, the 76ers' offensive style plays right into the Celtics' hands.

Boston has probably the best Embiid defenders in the league and Horford and Baynes, the latter of which did not even play in either of the last two meetings but has gotten into Embiid's head in the past. Also, Simmons' impact is severely mitigated against the C's, as the Celtics have a way of defending him that takes away his passing angles and forces him to beat them with his own offense.

Jaylen Brown, Celtics
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The 76ers are incredibly talented, and on paper, they are surely formidable, but they are not a significant threat to the Celtics. Again, not only is Boston simply a better team, but its mentality is very different. Guys like Marcus Smart, Marcus Morris and even Horford; those guys are killers. Embiid and Simmons? They are more worried about complaining to the media when things don't go their way.

It's that mental edge that gives the Celtics a huge advantage over the 76ers, and it's hard to see that changing any time soon.