The Philadelphia 76ers, over the past five seasons, have had their fair share of struggles against the Boston Celtics in the playoffs. Thus, it wasn't a surprise to see that the Celtics entered their second-round matchup as the favorite to advance to the Eastern Conference Finals. But heading into Game 6, it was the Sixers that had the golden opportunity to knock off their archrivals, as they took a 3-2 series lead heading into the friendly confines of Wells Fargo Center.

But it simply wasn't the Sixers' night. Shots simply wouldn't go down for the home team; among all the players that saw the floor, only one player shot above 50 percent from the field, and that was Georges Niang, a man who attempted just three shots (making two of them).

The story of the series thus far has been the play of James Harden. As simplistic as this sounds, when Harden plays like the best version of himself, the Celtics have struggled coping with him. This was the case in Games 1 and 4, when Harden made one difficult shot after another culminating in a go-ahead shot that gave the Sixers the win. Meanwhile in Game 5, Harden may not have had the best scoring night, but his steadiness as the floor general allowed the Sixers to catch a strong rhythm offensively, as he ended the night with double-digit assists.

However, during the Sixers' losses in the series, Harden missed double-digit shots, going 2-14, 3-14, and 4-16 in those games. Surely, a good Harden game is looking like Philadelphia's win condition in this series.

Nevertheless, James Harden is too good to be an X-factor. Given his pedigree as a player, it's his responsibility to show up with everything to play for.

With that said, here is the Sixers' ultimate X-factor in Game 7, as him showing up on both ends of the floor makes the lives of Joel Embiid and the rest of Philly that much easier.

Sixers' Game 7 X-factor vs. Celtics: Tobias Harris

Tobias Harris looks the part of the wing every contending NBA team needs. He stands at 6'8, he has a strong upper-body and he's quick enough, making him such a versatile asset on the defensive end. There's a reason why he's logging quite the heavy minutes workload for the Sixers. Harris, along with PJ Tucker, allows the Sixers to at least make life a bit difficult for Jayson Tatum and Jaylen Brown.

And Harris has done wonders for the Sixers defensively in this series as the primary defender on the Celtics' best player. Tatum has had some great moments for the Celtics; his heroics during the fourth quarter of Game 6 come to mind immediately. But overall, Tatum hasn't had the best of series. The Celtics star had a dreadful 1-7 outing in Game 2, and he struggled to score in the first half of Game 5 with the Sixers threatening to blow that game wide open (which they eventually did).

And to top it all off, Tobias Harris held Jayson Tatum to a dreadful 1-13 shooting night in the first three quarters of Game 6, not a mean feat for someone who isn't necessarily a defensive specialist.

However, given Harris' remuneration, he simply has to do more for a Sixers team that was crying out for a hero on the offensive end during their closeout attempt at home on Thursday night.

Tobias Harris scored just two points on 1-7 shooting from the field (0-1 from deep) in Game 6; there are no two ways about it, that is a terrible performance, especially for the Sixers' second-highest paid player. Perhaps Harris' defensive duties have been wearing him out to the point of complete offensive disappearance, but it's not like the Sixers will call upon him to shoulder a heavy offensive burden.

Simply put, Harris has to make the most out of the limited shots he's going to get. Tyrese Maxey's emergence as a stellar offensive force has relegated Harris to a fourth-option role, and it's not always the easiest adjustment for a player used to taking double-digit shot attempts per game to suddenly play a smaller part in the offense.

It's not like the Sixers need Harris to suddenly play the game of his life for them to win. The onus to carry them to victory will fall on league MVP Joel Embiid and James Harden's shoulders. But Harris role as a connective member of the roster on both ends of the floor means that a good game for him makes it easier for the Sixers to claim victory. A good game from Harris will give Harden and Embiid even more space to operate, which will be crucial to the Sixers' chances of winning Game 7 against the Celtics on the road.