The time has finally arrived, after a crazy rollercoaster of a regular season the playoffs are upon us. On Monday the Sixers will kick off their first-round series against the Boston Celtics. Although the Sixers find themself as the underdog, this is a series they could potentially pull an upset on.

One thing the Sixers have in their favor is they won the matchup in the regular season. The Sixers won three of the four games these two teams played this season. The games could have gone either way though. The Sixers averaged 106.5 PPG against the Celtics and the Celtics averaged 104 PPG against the Sixers.

Players to watch: Jayson Tatum (23.4 PPG, 7.0 RPG, 3.0 APG), Jaylen Brown (20.3 PPG, 6.4 RPG, 2.1 APG), Kemba Walker (20.4 PPG, 3.9 RPG, 4.8 APG) 

This is a series where the Sixers are going to miss Ben Simmons. The Celtics’ three-headed monster of wing threats has the potential to give the Sixers some trouble. Something the Sixers did well against the Celtics this year is defend Jayson Tatum.

Tatum averaged 19 points per game against the Sixers this year and shot just 33% from the field. A big part of that has to do with Ben Simmons, but the Sixers have shown they can slow down the Celtics’ star. Containing Tatum in this series is going to be a must if the Sixers want to advance to the conference semifinals.

Keys to victory: Joel Embiid and the size advantage 

The Sixers are only going to go as far as Joel Embiid can take them in this series. With no Ben Simmons, the team is going to need Embiid to lead the charge if they are going to advance to the next round. Luckily for the Sixers, this is a matchup where Embiid should dominate.

In the four games against Boston this year Embiid is averaging 21.3 PPG, 10.3 RPG, and 3.3 APG in just under 28 minutes of action each game. If Brett Brown can play Embiid close to 38 minutes as he has said in the past, the All-Star center should leave his mark all over this series.

The Boston Celtics do not have the size to match up against the Sixers’ lineup, and it is something the Sixers need to exploit. One thing the Sixers did great against the Celtics was rebound. In the season series, the Sixers averaged around 12 more rebounds a game.

Joel Embiid needs to take big advantage of the size disparity. We saw in the seeding games that he has punished teams for going small on him, and he should look to do more of the same in this series. One thing he will need to focus on is operating well out of double-teams because Celtics' head coach Brad Stevens will have tricks up his sleeve to defend the All-Star center.

What to do with Al Horford 

Al Horford has played well in the bubble since being reinserted into the starting lineup, but this is not the most favorable matchup for the veteran big man. Mainly the issues with Horford starting come on the defensive side of the ball.

With the Celtics running a smaller lineup it could lead to matchup complications for Horford. He hasn’t been the greatest defending on the perimeter this season, so Brett Brown might have to think about sliding Horford back to the bench.

This could allow Matisse Thybulle or Glenn Robinson III to run with the starters and add stronger perimeter defense. Starting Thybulle to defend Jayson Tatum might be the most beneficial scenario for the Sixers.

Depth factor

Depth is always a key factor to a team making a serious run in the postseason, and in this series, the Sixers arguably have the edge in depth. The Celtics do not have many threats off the bench and their second unit could get weaker if they lose Gordon Hayward in this series.

The Sixers are going to have to make the most of the advantage in the second unit. Most importantly Alec Burks, who has been lethal for the Sixers off the bench. If Al Horford does indeed slide to the second unit it only makes the second unit stronger. Winning the battle when the stars are off the floor could sway the series in the Sixers’ favor.

Realistically this is a series that could go either way. It is all going to come down to who makes the most of their advantages.

If the Sixers can contain the Celtics’ wing players and Joel Embiid dominates in the post the Sixers could see themselves in the next round. It is going to be an uphill battle, but one the Sixers could potentially win.

Kevin McCormick is the 76ers insider for 97.3 ESPN and 76ers editor for Sportstalkphilly.com. Follow him on Twitter @KevinMcC973.