All it takes is one look at the Sixers’ potential defensive matchups against the Raptors to understand why the Eastern Conference semifinals offer Brett Brown a daunting challenge.

Here are three matchups that could determine the series:

Tobias Harris vs. Pascal Siakam

This is one of those matchups that should shine a bright light on the Sixers’ roster-building ability over the last few seasons. The Raptors selected Siakam at No. 27 overall in 2016, one pick after the Sixers took Furkan Korkmaz. After steady improvement in his first two seasons, Siakam has exploded in his third season, establishing himself as a potential difference-maker in this series.

In the Raptors’ five-game series win over the Magic in the first round, the 6-foot-9 four-man averaged 22.6 points and 8.4 rebounds and shot .364 from three-point range on 4.4 attempts per game.

Siakam’s game might not be as polished as Harris’, but he is stronger and more athletic, and the emergence of his outside shot could pose a significant challenge for Harris when coupled with his nonstop motor and aggressiveness in getting to the rim.

He’s been equally good on the defensive side of the ball. Among power forwards who averaged at least 20 minutes, Siakam ranked sixth in the NBA in ESPN’s defensive Real Plus-Minus metric, trailing only Draymond Green, Giannis Antetokounmpo, Anthony Davis, Paul Millsap and Derrick Favors. The Raptors defense was 5.4 points better per 100 possessions with Siakam on the court than with him on the bench.

While the Sixers have a couple of defenders in Jimmy Butler and Ben Simmons who were elite against the Nets, and who have the skill set to mark Siakam, they’re going to have their hands full against Kawhi Leonard and Kyle Lowry.

Jimmy Butler and Ben Simmons vs. Kawhi Leonard and Kyle Lowry

An interesting note from the regular season: The Sixers outscored the Raptors, 215-213, in the 92 minutes that Butler and Leonard were on the court together. The Raptors outscored the Sixers, 30-20, in the 14 minutes that Leonard was on the court and Butler was off it.

In the Raptors’ most recent win, Simmons and Butler spent an even amount of time guarding Leonard and Lowry. There’s reason to believe that they can hold their own, given what we saw out of both of them against the Nets’ dynamic perimeter attack. Which is why Harris vs. Siakam was No. 1 on this list.

That could leave the Sixers needing to even things out on the offensive end, with Butler needing to attack Danny Green if Leonard draws primary duties on Simmons (assuming Lowry chases J.J. Redick).

In his four games against the Raptors this season, Simmons has turned the ball over 25 times and had 35 assists. By comparison, Simmons turned the ball over just 15 times in five games against the Nets. Simmons’ 10.1 attempts from the field against the Raptors are two fewer than his season average and one fewer than he averaged in the Nets series.

Joel Embiid vs. Marc Gasol

Here’s a daunting factoid: In five career games in which Marc Gasol was the opposing starting center, Joel Embiid has never scored more than 18 points. In two games against Gasol this season, Embiid is 8-for-28 from the field with 10 turnovers and two blocked shots.

Joel Embiid in games started by Marc Gasol
Joel Embiid overall

Gasol will present a huge challenge on the offensive end if the Raptors use him to draw Embiid away from the rim. Gasol is a career 35 percent shooter from three-point range and has averaged 1.3 makes on 2.9 attempts per game since joining the Raptors. In two games against the Sixers this season, both with the Grizzlies, Gasol is 5-for-10 from three-point range.

Over the last two seasons, the Sixers have averaged just 99.4 points per 48 minutes when Embiid and Gasol are on the court together, compared with 125.1 when Embiid is on and Gasol is off. Defensively, they held the Grizzlies to 92.2 points per 48 when Gasol and Embiid were on the court vs. 97.7 when Embiid was on and Gasol was off. In two games against the Grizzlies this season, the Sixers had an Offensive Rating of just 96.9 when Embiid and Gasol were on the court together (although it’s worth noting that the Sixers shot just 19 percent from three-point range during those stretches, including an 0-for-9 from Landry Shamet).

Marc Gasol in games started by Joel Embiid
Marc Gasol overall

Though the Sixers have lost six of eight games to Toronto dating to last season, this playoff series will be the first time that either of these teams faces the other at what currently constitutes full strength. The Sixers’ 126-101 win on Dec. 22 came on a night when Toronto was playing without Leonard and its top two big men. Likewise, the Raptors’ 119-117 win on Feb. 5 came without Redick or Harris in the lineup, a significant fact when you consider that the Sixers shot just 7-for-24 from three-point range and featured an eight-man rotation in which T.J. McConnell and Furkan Korkmaz combined for 42 minutes. McConnell finished at -9, Korkmaz at -14.

Of the 960 player minutes the Sixers logged against the Raptors during the regular season, nearly half — 49.4 percent — were accounted for by players who are not projected to be in the rotation this series.

But even with Harris now in the fold, there aren’t many easy answers as the Sixers look to match up with a Raptors starting five that outscored the Magic by 86 points when it was on the court together in the first round.