CAMBRIDGE, Mass. — It didn't feel like the eve of a must-win game. It felt like an Ivy League gymnasium with an undersized three-point line and a bunch of oversized players approximating the professional distance. This was Sixers practice on Tuesday afternoon: not exactly business as usual, given the setting, but hardly the base camp of a team under siege.

There might not be a phrase in the sports writer's lexicon more overused than the one you saw at the top. Must-win. It's a nebulous term that gets arbitrarily assigned to heighten a game's dramatic tension. Granted, the numbers say that a team that falls behind 2-0 ends up losing the series 93 percent of the time (per Oddshark.com). But the Celtics were up 2-0 last series, and the Bucks still ended up winning three of the next four to force a Game 7. Now, clearly, the seventh game of a seven-game series warrants the moniker, "must-win." But what does that mean for Game 2? Logically, a team cannot lose two must-win games in the same series.

But enough word-parsing. By the end of Thursday night, we'll have a very good idea about whether this Sixers run will extend another round. It's still about process at this point. Regardless of the end result, we need to see a different team.

First and foremost, we need to see if Brett Brown can find a way to get Joel Embiid comfortable on defense because the big man's presence around the rim was always the biggest reason to think that the Sixers would win this series. Problem is, Brad Stevens did a good job of forcing Embiid away from the rim by keeping his big men away from it. It certainly helped matters that he had a trio of big men capable of shooting a combined 5-for-10 from downtown, but that's not the whole story. In addition to the four three-pointers that Aron Baynes and Al Horford knocked down, there were at least two other Celtics threes that came from territory that appeared to be the responsibility of Embiid's spot in the Sixers' defensive shell. The big man acknowledged his lapses after the game, using the adjectivized form of a synonym for fecal matter that rhymes with "pretty." But he also expressed some frustration at the situation the Celtics put him in.

What adjustments is Brett Brown going to make headed into Game 2?
YONG KIM / Staff Photographer
What adjustments is Brett Brown going to make headed into Game 2?

"My job is to make sure the ball stays in front of me," he said, and that's true, and you can empathize with his plight on a play like the one that gave the Celtics a 103-90 lead with 4:56 remaining. Embiid was at the top of the key guarding Horford as Marcus Morris posted up Marco Belinelli on the left wing. After the entry pass, JJ Redick left his man to offer baseline help to the outsized Belinelli, while Horford cut to the basket. As Embiid drifted back to his natural home in the paint, Terry Rozier moved from the weak-side corner to fill Horford's spot, and Embiid could not get back in time to contest the shot.

These are the types of plays that the Sixers have spent the last couple of days attempting to troubleshoot. Some of what happened in Game 1 was outside of their control: the two pull-up threes Rozier hit in the first half, for instance. Similarly, Baynes entered the postseason having hit a total of four three-pointers in 376 NBA games (although he was 2-for-3 in the Celtics' first-round series against the Bucks).

The question of Game 2 is whether Brown can adjust his defense to prevent the Celtics from regularly finding or creating holes. Turn three of those makes into misses and suddenly it is a seven-point game with the Celtics shooting 40 percent from downtown. Then, turn three of the Sixers' misses into makes and they are up by two despite shooting 31 percent.

Regarding the second part of that equation, I counted five wide-open misses by the Sixers over the course of the game, with five more that were good looks. It doesn't seem like too tall of an order for three of those 10 shots to go in instead of out.

Yet none of those coulda-wouldas should diminish the dose of reality that Game 1 delivered. With Horford, Rozier and Jayson Tatum, the Celtics have a trio that collectively poses some serious matchup dilemmas for the Sixers.

"To me, there is a balance between overthinking it — overcoaching it — and letting them play free," Brown said.

At this juncture in Round 1, we heard a lot of boxing analogies about what the first game of a series reveals. The Sixers having two things going for them right now: They've experienced the skill set of their opponent firsthand, and they've had two days to prepare for the fighting style they must defend. Game 2 might not reveal the winner of the series, but it should tell us whether the Celtics are definitively the better team.