With Gordon Hayward back to 100 percent and Kyrie Irving looking like his old self in pick-up games, the Boston Celtics are set to be absolutely loaded this season. When Danny Ainge made the trade for Irving last summer, he said he fit Boston's timeline to win. Well, that time is now. 

Just run up and down this almost perfectly constructed modern roster: Length everywhere, and the enviable defensive versatility that comes with it. Scoring, both in the form of multiple one-on-one creators and a movement-based system with one of the best passing bigs in the league as a hub. Shooting. Incredible depth. Elite coaching. It's all there on this team. The Celtics are the clear favorite in the East and a legit threat to beat anyone that comes out of the West in a seven-game series, including Golden State. 

That said, there are questions for every team. 

Here are four facing the Celtics.

What's the cost of starting small?

With Gordon Hayward's return to action, someone from last season's most commonly used starting lineup -- Kyrie Irving, Jaylen Brown, Jayson Tatum, Al Horford and Aron Baynes -- is headed for the bench. Most assume Baynes will draw the short stick, Indeed, Brad Stevens started last season with Irving, Hayward, Tatum, Brown and Horford for the roughly five minutes Hayward was available to him. Just about everything about this lineup looks like a monster. 

Except, perhaps, rebounding. 

Two years ago, when they were being led by Isaiah Thomas as something of a super-try-hard team that out-kicked its coverage all the way to the Eastern Conference finals, the Celtics were one of the five worst rebounding teams in the league, and it was one of the reasons nobody ever really believed they were an actual elite team. 

Last season, Boston vaulted to 11th league-wide on the defensive glass, and the two-big combo of Baynes and Horford had a lot to do with it. Both guys secured just under 22 percent of the available rebounds when they were on the floor, which is a good-but-not-elite individual number. The key is what they do when playing together. Last season, Boston deployed four different lineups that played at least 100 minutes together. Two of those lineups had a plus-double-digit net rating. Horford and Baynes were in both of them. 

Digging deeper, the defensive ratings of those two lineups were an elite 98.3 and 92.2, respectively. In short, a team that has both Horford and Baynes on the floor is going to be a good rebounding team and a great defensive team, given Boston's parts. Now, a lineup that swaps Hayward for Baynes, of course, has plenty of its own merits, and the offensive uptick could well cancel out the potential rebounding downgrade. Surely the Celtics will monitor this, and it could become a matchup-dependent decision for Stevens. 

Ultimately, a lineup of Irving, Brown, Hayward, Tatum and Horford looks a lot like the Warriors' vaunted Death Lineup of Steph Curry, Klay Thompson, Andre Iguodala, Kevin Durant and Draymond Green. It's all about size and versatility with multiple playmakers that gang rebound and push the pace. But as most are aware, the Warriors do not start this lineup. They finish with it. Playing that small consistently can tax you pretty hard on the defensive end and on the glass. 

The Celtics will likely start with their small lineup, and it will be a monster in many ways. But it does come at a cost. Just something to keep in mind.

What is the Smartest finishing lineup?

Boston re-signed Marcus Smart this summer on a four-year, $52 million deal -- yet it may be Smart who ends up feeling the minutes crunch that Hayward's return will bring. We already know Smart won't be starting. The question is: Will he be finishing? In today's NBA, that's really all that matters. Who's on the floor in winning time? 

Smart has been a fixture in Stevens' finishing lineups, and for good reason. Last season his plus-7.8 net rating in clutch time (defined as a five-point game with under five minutes to play) was second only to Jayson Tatum among Boston players with significant time in those situations. In last year's playoffs, obviously when it counts the most, Smart was a part of Boston's most successful fourth-quarter lineup -- (Terry Rozier, Smart, Tatum, Marcus Morris and Horford) -- which was a plus-33.9 per 100 minutes. As long as we're cherry-picking numbers, Smart also had the best individual defensive rating in the fourth quarter among Celtics regulars. 

Now, we all know numbers can be deceiving, and frankly, Smart's impact goes well beyond numbers, including his historically awful shooting percentages. The guy is just a flat-out winner, mainly for his defense but also for his knack for timely shot-making and his ability to make plays for teammates and draw defensive attention that belies his inability to shoot. It doesn't make a lot of sense that defenders stay glued to him unless you put stock in his willingness to shoot over his actual ability to shoot, and a lot of people do believe that. If you're not afraid to shoot, defenders will guard you. It's a basketball instinct. 

Either way, Smart has proven, at times against seemingly all statistical odds, that he deserves the full trust (or something close to it) of Stevens in the most critical stretches of games. Still, only five guys can play. In the cases where Stevens leans on his likely starting lineup of Irving, Brown, Hayward, Tatum and Horford to close games as well, Smart will be the odd man out. On the flip side, there could also be times, whether in particular matchups or simply during certain games when Smart has it rolling in terms of total impact, that Stevens will choose to ride Smart. And in those situations, who comes out? 

That question, in turn, raises this next question ...

What is the Hayward-Tatum-Brown hierarchy?

There isn't a lineup in the league that boasts three more interchangeable players than these three. It's a huge luxury in terms of the versatility they provide, not to mention the insurance against injury to one of them -- but it also could, under certain circumstances, become one of those good problems where it actually becomes nearly impossible to decide which guy draws the short straw should there come a time when the Celtics are fully healthy and Smart is playing in a manner that forces Stevens to keep him on the floor late in games. 

Seriously, who gets the hook out of these three?

It's a question that goes beyond just potential playing time and into, perhaps, the realm of Boston's future plans. There is a way for Danny Ainge to play all these guys, but there's this sort of unspoken debate as to who would be the most available player should the Celtics ever get serious about acquiring another star via trade, which they're always a threat to do. Tatum is generally considered untouchable. Hayward probably wouldn't have quite the value given his age and contract. Brown feels like the third wheel here. 

Man, what a team you're putting on the floor when Jaylen Brown is your third-best wing and probably the first candidate to move to the bench should Stevens elect to start big with Baynes, or finish with Smart. Brown is so good. Given minutes and opportunity, he could be an All-Star this season. No question. 

Chances are, none of this will become much of a problem. There will be injuries. Stevens will balance the minutes in the brilliant way he does everything else. But again, in the perfect world of everyone being healthy and Smart making his jumpers, someone is going to get bumped. Also keep in mind, this is to say nothing of Rozier and/or Marcus Morris, who likely won't crack the top-six in the regular rotation but are both more than capable of getting hot enough on any given night to force themselves into the closing lineup, which brings up another layer of decision making for Stevens. 

Any coach in the world would sign up for these kinds of decisions, but they are still decisions. You can look at it in two ways: Stevens either can't make the wrong one, or he can't make the right one. 

Can Kyrie hold up in isolation defense?

OK, let's look at a scenario where Stevens wants Hayward, Tatum and Brown on the floor, and alongside them he decides Smart has to stay on the floor. Assuming you want to keep on traditional big out there, Kyrie Irving would become the odd man out. I have to admit, there's a part of me that wants to dream about a closing lineup that puts Smart at the point with Brown, Hayward, Tatum and Horford. I have no idea how you would score on that lineup, and you could still have plenty of offense. 

That said, it's nearly impossible to imagine Kyrie not finishing games. He's arguably the best one-on-one creator in the league, and that is vitally important down the stretch of games when teams switch even more and offensive "systems" tend to stall out. Kyrie is going to be on the court. Considering the alternative is merely an exercise. 

The trade-off of having Kyrie in there instead of Smart, or perhaps instead of one of the wings, is defense, and teams will surely be trying to exploit Irving on the defensive end in much the same way teams go at Stephen Curry -- not so much because Curry's a particularly poor defender, but simply because the other Warriors on the floor are elite. Boston will have four defenders of switchable length and athleticism, and Irving, an average isolation defender at best, will get spotlighted by default. Can he hold up? 

Surely Boston will have some maneuvers to keep Irving from getting switched onto bigger ball-handlers, or to double quickly and force the ball out of his man's hands and rely on their length and athleticism to rotate and recover, but at some point it's inevitable that Irving will simply have to buckle down and guard a bigger, stronger, more athletic offensive player, much like when Curry has to man up against a LeBron James or Russell Westbrook or whoever it may be. Even if it's only a couple possessions over the final few minutes, those possessions decide games. 

So these are good problems, yes?

No. They are great problems. I'm just saying keep an eye on these things because they will be a fascinating study in talent deployment, and frankly, because there isn't much else to worry about with this Celtics team, which by any standard of evaluation is going to be so freaking good. Thing is: being this good is a burden of its own kind. There is no more grace period while LeBron James reigns supreme out East. The King has gone West. The throne is open. The time is now. 

In the end, one of these decisions about who plays, and when, could end up being the difference between going to -- and possibly winning -- the NBA Finals and falling short to a team, like, say, Toronto or Philly before Boston even gets any farther than it did last season. Stevens will have a nightly decision on his hands how to allocate his troops, and he'll use the regular season to learn as much about how certain guys play together to inform his lineup deployments come playoff time. 

These are all big names, but remember, Brett Brown sat Ben Simmons in last year's playoffs for T.J. McConnell. Tough decisions have to be made and your name doesn't matter when it comes down to it. This is going to be pretty fascinating to watch play out as guys who are used to being the star have to potentially bite the bullet in the name of chasing a championship.