After Boston Celtics coach Brad Stevens scribbled up a series of successful after-timeout plays to help his team steal Game 3 of the Eastern Conference finals on Sunday, Celtics big man Al Horford was asked how many points per game Stevens might be worth.

"A lot," Horford said, smiling.

Stevens has drawn acclaim from his players and the Cleveland Cavaliers this series for his role in keeping Boston competitive despite the loss of Isaiah Thomas. LeBron James has often gushed about Stevens' after-timeout sets, repeatedly offering unsolicited praise.

Even after the Cavaliers rallied to win Game 4, James noted how Stevens has "kind of been killing us on ATOs."

All of which left us wondering: Just how valuable is Stevens? Stevens' ATO sets, by his own admission, are not always the most complex, but he seems to have an encyclopedic knowledge of possible plays and a knack for anticipating how the opposition will react to each sequence.

This was highlighted in Game 3 when Stevens drew up a simple action that left Avery Bradley open to hit a game-winning 3-pointer with 0.1 seconds to play.

"He's very good out of ATOs," James said. "He has so many different wrinkles, misdirection. [You're] thinking the ball is going this way, he has a misdirection going the other way. You've got to kind of keep your head on a swivel. He has a lot of packages. So you can plan for a few, but then he might run something you've never seen before."

With Thomas shut down for the season after aggravating a lingering hip ailment in Game 2 of this series, the Celtics clearly lack the star power of the Cavaliers. It's a big reason why Boston finds itself in a 3-1 series hole and fighting to extend its season with Thursday's Game 5 at TD Garden.

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Boston's biggest star at the moment might just be Stevens.

The absence of Thomas has put an even greater spotlight on Stevens' ability to draw up plays. The Celtics are averaging 1.156 points per play on ATOs (37 points on 32 possessions) over the past two games, according to Synergy Sports data. For sake of comparison, the Houston Rockets led the NBA in ATO efficiency during the regular season, averaging 1.017 points per play.

The Celtics finished third overall in the regular season, trailing only the Rockets and Cavaliers, while averaging 0.978 points per play, according to Synergy data. Boston's total of 1,222 points generated off ATOs was easily the highest in the NBA.

"[Stevens is] really good," Horford said. "His ability to pick up on little things on the floor that nobody really sees and exploiting them, he's just great at that. He sees things that we don't see, things that make a big difference. He did it all through [Game 3].

"You've got to kind of keep your head on a swivel. He has a lot of packages. So you can plan for a few, but then he might run something you've never seen before."

"Our last, I think, three baskets were ATOs that he drew, and they were just great because the defense didn't know it was coming -- and we didn't really know it was coming when he drew it up. A lot of the time we'll go through stuff in shootaround, plays for the end of the game, but he didn't draw those up then, he just kinda came up with that on the fly and he made adjustments. That makes him special."

Stevens has downplayed his wizardry, repeatedly noting that most of his sets are simply tweaked versions of plays he has seen other teams run. Last March, Stevens said, "Honest to God, I've stolen everything we've ever done from somebody else."

His counterparts still rave about his game management. Cavs coach Ty Lue suggested Tuesday that a Thomas-less Boston is harder to game plan for than the Golden State Warriors. San Antonio Spurs coach Gregg Popovich has said he still watches old Butler film to steal plays that Stevens ran at the college level.

Stevens is the first to admit that ATO success ultimately hinges on his guys making the right plays. If Bradley, Horford and Jonas Jerebko don't knock down late-game shots in Game 3, Stevens probably isn't being toasted in the aftermath.

Remember, too, that just last season the Celtics were head-scratchingly poor at ATOs. Boston ranked 27th in the NBA at 0.82 points per play, though their numbers in the second half of the season were more in line with the lofty marks that Stevens has typically produced over the past three seasons (Boston ranked ninth overall in ATO points per play during the 2014-15 season).

To get a rough estimate of just how many points per game Boston's ATO success is adding, we took Boston's 0.978 points per play and subtract the league average this season (.905), then multiplied that number by the league's average number of ATOs (1,213). Call it VORC -- value over replacement coach -- but Boston generated an extra 89 points over a league-average coach, or 1.1 points per game.

Still, it's nearly impossible to create a metric that can accurately monitor the value of a coach, if only because of all the variables a head coach controls (lineups, rotation, philosophies) and the immeasurable impact a coach might have on his team simply based on his demeanor.

It's Stevens calm sideline manner that has further endeared him to casual observers. While he most certainly has moments of emotional outburst -- he was livid when Crowder strayed from J.R. Smith in a key late-game sequence in Game 3 -- Stevens has an ability to quickly turn his focus to the next possession rather than dwell on something he cannot change.

ESPN's Jeremias Engelmann, the brains behind our Real Plus/Minus (RPM), has a similar metric dubbed Coach RAPM that attempts to quantify the value of head coaches. Engelmann crunched the numbers and relayed that Stevens ranks 44th among the 133 NBA coaches in the league since the 2001 season. Among active coaches, Stevens still sits just 18th out of 30.

How exactly is that possible?

Engelmann explained how additions such as Jae Crowder and Amir Johnson -- plus/minus darlings -- have made it more difficult for Boston to exceed the anticipated result. Engelmann believes Celtics president of basketball operations Danny Ainge deserves much of the credit for Boston's increase in wins for putting the right pieces together.

Still, it's hard to ignore the buzz around Stevens, especially those that have come to Boston in large part because of his presence. It's fair to wonder if Stevens will be key in luring a marquee free agent to Boston this summer (hey there, old friend Gordon Hayward) and improving Boston's chances to compete with Cleveland in the near future.

"Brad's a genius," said Gerald Green, who signed with Boston for the veterans minimum in the summer, played sparingly and emerged as a key playoff contributor in the Chicago series. "I said it -- he's one of the reasons why I came here. I've always heard about his really, really, really high IQ of knowing the game. He's a genius."