SAN ANTONIO -- It's probably not fair to call the Boston Celtics the season's biggest surprise. They have two All-Stars, Kyrie Irving and Al Horford, playing some of their best basketball ever. They are long, athletic and talented with a starting lineup that boasts four former top-three picks. They have the league's brightest young coach and a roster stocked with quality pickups.

Even without injured star Gordon Hayward, the Celtics are no underdog story. But considering their youth and lack of roster continuity, what they've done without Hayward is remarkable. It's enough to wonder just how powerful his return will make them.

"It's actually too bad that Hayward's gone," Spurs head coach Gregg Popovich said Friday night before beating the Celtics in a thriller, 105-102. "Because then you could really see what they can do."

In some ways the Celtics will benefit from Hayward's absence, which could extend through the rest of the season. Jayson Tatum and Jaylen Brown have blossomed with increased responsibilities. Irving has needed to figure everything out without one of his prime safety valves (that process didn't take long, did it?). Further down the roster, a number of youngsters, including Semi Ojeleye, have gained more experience than they would have with a fully healthy roster.

But even with the Celtics sitting atop the Eastern Conference standings, the thrilling question awaits its answer: What will they look like with Hayward?

"Honestly, I haven't really thought about it," said Horford. "For me mentally, in order for us to keep moving forward with the season and just focusing on what we have, I try to focus on our group."

"Now that you mention it," the big man continued, a smile spilling over his face, "I think that we'll just be very explosive. I mean, we kind of have that now, but with him he just adds a whole other dimension. Because his ability to shoot 3s, shoot them really well, but also attack the basket, defend. One through five can shoot threes, can put it down, can post. We have a very versatile group. So I think it will be very scary once he's able to come back."

Hayward checks all the boxes for what the Celtics need. Their defense, built for versatility, will have even more of it. They'll be able to stagger their All-Stars to carry anti-scoring bench units. With Hayward, Boston's starting lineup should easily be one of the league's best. It's possible that group will feature five 40-percent or better 3-point shooters, with all plus athletes, including four long guys at least 6-foot-7. Holy hell, Irving-Brown-Hayward-Tatum-Horford should be dynamic.

"I feel like he's built into the system," Horford said. "His strengths are what (the Celtics value). In the preseason, in the short time that we had him, in practice and everything, you could already tell that he was going to just blossom because his ability to shoot the 3-ball, but also he can play pick-and-roll, he can post the ball up, and he's a great defender. So that's what we take a lot of pride in is defending and then being able to have skill on the offensive end. So he's the perfect fit for this offense."

The Celtics won't find out exactly what they have until Hayward works his way back into the lineup. For now, Boston fans will have to settle for one of the youngest, most exciting, and best teams in the league.

"I think the biggest thing is that we have a job to do," Stevens said. "We can compartmentalize how we feel, our empathy for Gordon, and when we see him and we're not on game days, or when we text on game days or whatever, it's still more about him and his health.

"But also then you have to say, 'OK, what do we have to do to be successful?' And I think that we talked about we knew we were young but that doesn't really matter. We've got guys that those guys can lean on and play off of. So we just have to figure out what we do best and how to put ourselves in position to give ourselves a chance at success. It doesn't mean you're going to have it. I mean we've come back from a bunch of games we probably shouldn't have won. But you just want a chance."

The Celtics do have a chance now, but Hayward could unlock so much more than that.