On Aug. 28 at St. Bernard High School in Los Angeles, about two dozen scouts, players, and trainers watched as Gordon Hayward and Bradley Beal lined up to play one-on-one.

It was Hayward's first time playing one-on-one against an NBA starter since undergoing an unexpected second surgery in late May to remove a plate and screws from around the left ankle Hayward shattered five minutes into his Celtics career. The discovery that he needed another surgery had devastated Hayward. It threw his rehabilitation timetable into disarray. By Aug. 28, he was supposed to have been months into five-on-five games against NBA competition. Now, he was easing into one-on-one.

"I wasn't thinking 'I'm gonna kill this guy,'" Hayward told ESPN.com Tuesday night, after another disappointing preseason game for the Celtics. "I was thinking it would show me what I needed to work on."

Beal told Drew Hanlen, the popular skills trainer who holds court at St. Bernard and tinkered with Hayward's game over the summer, that he was confident.

They started from the post, and could only dribble twice before shooting. Then they moved to the perimeter and allowed themselves three dribbles.

Hayward swept five straight games. "He surprised the hell out of me," Beal says. Beal called Mark Bartelstein, the agent who represents both.

"I have good news and bad news," Beal said, the two recalled. "I might suck, but Gordon is 100 percent back."

It was a watershed moment for Hayward -- a glimpse of hope after a year of arduous rehab, intense anxiety, and the gut punch of a second operation.

"I was definitely surprised," Hayward says. "There had been so many low moments. That was a huge, huge confidence booster." Editor's Picks Lowe Post: Arnovitz on the five most confusing teams

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Bullying Beal was a great sign. Hanlen and Hayward knew defenses would switch against Boston's best lineups. They spent much of the summer working on posting up smaller players.

But relying on one-on-one work as September approached was also a reminder of how far behind Hayward was. It is showing so far in the preseason. Hayward is just 5-of-20 from the floor, and has committed eight fouls in 59 minutes.

"Physically, I feel pretty good," Hayward says. "But I don't feel comfortable on the floor yet. It's one thing to be physically able to do everything. It's another to be a basketball player -- the timing and the rhythms. When you've been playing a long time, you just know. But not after you take a huge break, and come back to a new system. The second surgery was such a setback. I was really looking forward to playing 5-on-5 the whole summer. What I'm going through now is what I wanted to do in the summer, but it didn't work out that way."

Hayward had just started to run full speed and play one-on-one in late May, when doctors concluded it was best to remove the plate and screws. Hayward had been feeling pain around his ankle for months. He agitated for the surgery earlier, fearing an operation in May or June would sabotage his summer. "Hindsight is 20/20," he says, "but I wish we had knocked this out in March."

Doctors and Celtics officials cautioned that no one should undergo a second operation if they don't absolutely have to, Hayward recalls. They needed to determine if something other than the plate -- some issue that would go away -- was causing the irritation. That process took time.

"I was miserable," Hayward says. "To go back into a walking boot after all that progress -- back on crutches. That was my lowest moment."

"I felt terrible for him," says Danny Ainge, Boston's GM.

Hayward's lows can get really low. "That's how I'm wired," he says. "I stress and stress."

People close to him have long known to expect calls from a despondent Hayward after so-so games. Hayward has trouble sleeping on those nights, he says. Friends hoped the year away would change that. He would miss the game, rediscover the joy of it, fixate less on mistakes. Perhaps the Celtics' success without him would ease Hayward's self-imposed pressure upon his return.

"It's just basketball," says Jason Smeathers, a trainer who is among Hayward's closest friends and lived with him for most of the last year. "On this team, you are allowed to have a bad game."

Hayward tried to internalize that. Sometimes it worked. Sometimes it hurt to watch Boston thrive without him. "When you go down like I did after changing teams -- it's just not supposed to happen that way," he says. "It's just the nature of being a competitor. You want to feel like you're missed. And I was missed. But when you watch them rattle off 16 in a row, those negative thoughts creep in. It was tough sitting and watching."

Right now, it's tough playing. On the way home from Sunday's game against Charlotte, in which Hayward shot 1-of-7 and committed five fouls in 21 minutes, he called Bartelstein to mope. Bartelstein told him to focus on his chase-down block of Jeremy Lamb -- proof he could get up, and then land hard on that left leg.

That was their routine during Hayward's year rebuilding his leg. Hayward would call Bartelstein and lament every setback -- the days he felt more pain; when it took him longer than usual to pluck marbles off the ground with this toes, a game he and Smeathers invented; when he took a small step backward on some test of balance or agility. After consoling Hayward, Bartelstein would phone Smeathers and the two other permanent members of Hayward's rehab crew -- Steve Mount, the Celtics' rehabilitation manager, and Tyler Yeaton, their strength and conditioning coach -- for their take on the day's work.

"I would get a completely different version from them," Bartelstein says. His conversations with Hayward always ended the same way: "I would give him s--- about being completely out of his mind," Bartelstein says. "But that perfectionism, dissecting everything a hundred times -- that's what makes him who he is."

"That perfectionism, dissecting everything a hundred times -- that's what makes him who he is," Hayward's agent Mark Bartelstein said. Kent Smith/NBAE via Getty Images

Hayward's competitive nature got him through the drudgery. We hear all the time about how professional athletes are manically competitive. They all hate losing at board games. Hayward is maniacal even by those standards. He turned every part of his rehabilitation into a competition.

Every morning over Starbucks, he and Smeathers would play a best-of-three series of the video game Clash Royale, with the winner earning the right to talk trash for the rest of the day. Hayward famously turned the marble-picking exercise into a timed race, and bet against anyone willing to challenge him in a contest of half-court shots attempted from a chair.

Hayward used various grip-strengthening exercises to distract himself during Celtics games. One favorite: unfold several pages of a newspaper, and pile them on top of each other. Place one hand in the middle, and using only that hand, attempt to crumple all of the paper up into a ball that fits in your palm. Sound easy?

"Dude," Hayward says, "it lights your hand on fire."

In January, Hayward decided it was time to put Smeathers, Yeaton, and Mount through some competition; he was tired of listening to them argue about who was the best athlete.

"He's a misery-loves-company kind of guy," Smeathers says.

Hayward created Gordon's Grand Gauntlet, a decathlon-esque set of events that included a mile run; a 100-yard dash; driving and putting contests; a test of who could throw a baseball farther; an endurance test on an exercise bike; and a trivia contest. Hayward wrote the questions himself.

"We were pretty f------ bored, really, is what it was," Hayward says, laughing.

When Mount and Smeathers pedaled the same virtual distance over three minutes on the resistance bike, Hayward made them start over. There had to be a distinct finishing order in each event. No ties.

During Hayward's pool work at Boston's old practice facility, Smeathers and Mount talked trash about who would win a swimming race. Hayward finally demanded they settle it. Mount won. Staffers set up a makeshift podium for a medal ceremony. Hayward found a way to have the Australian national anthem -- Mount is Australian -- blare as Mount draped a weight around his neck as a medal.

"You want to feel like you're missed. And I was missed. But when you watch them rattle off 16 in a row, those negative thoughts creep in. It was tough sitting and watching."

When Hayward needed breaks, he would take a Patriots practice football -- a gift from Tom Brady -- and heave it all over the Celtics facility, inventing contests with Smeathers: Who could sling the ball between those two lights hanging from the ceiling, and hit a target on the wall? The ball eventually got stuck in a light fixture. Hayward never retrieved it.

In late July, about two months after the plate-removal surgery, Hayward was finally ready to run full speed again. At a training facility called EXOS in San Diego, staffers set up a "beep test" run for him. Hayward was to run back and forth between two points, changing directions each time a beep sounded. The beeps start at infrequent intervals, so the runner can begin at a casual jog; the interval shrinks as the test proceeds. Anytime a beep beats the runner, the test ends. Smeathers watched to make sure Hayward didn't overexert himself.

Scott Morrison, a Celtics assistant visiting Hayward at the time, decided he would join. "If there was ever a chance to beat him at anything athletic, this was it," Morrison says. They went on and on, faster and faster. Smeathers was surprised Hayward was still going. Hayward was surprised Morrison was still going.

"There was absolutely no way I was losing to a 40-year-old," Hayward says. "It can't happen. Even if it was my first time running in a long time." (Morrison is 41, for the record.)

Morrison finally gave out. Hayward ran one last sprint, stopped, and gloated. "It was, 'OK, I won, that's enough,'" he says.

Today, it's ping-pong. Hayward has his own paddle. When he saw the pool table in the Celtics' new practice facility, he badgered staff about buying a ping-pong table-topper until they finally caved. Hayward supervised the purchasing of paddles, so that everyone would have good ones. He was undefeated until Mount secretly swiped Hayward's personal paddle, replaced it with a generic one, and beat him as much of the staff watched. Mount then revealed what he had done. Hayward has since been more careful.

Hayward wants to hang a whiteboard next to the table, where he can scribble updated ping-pong rankings.

This is how Hayward passed time during his rehab process. That is over now. The games are happening, and there is more to sort out than Hayward anticipated in January and February -- when his rehab was on course, when a second surgery was an unlikely worst-case scenario. NBArank: This year's best players Our prediction for the top players in 2018-19:

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"It's just rebuilding habits -- remembering the right time to cut, or how to guard a simple action," Brad Stevens, Boston's coach, tells ESPN.com. "Those are the things you don't think about when you're running, or playing one-on-one. Now you have this big 5-on-5 game to play. To my eyes, he looks fine physically."

The more complex layer: figuring out how Hayward fits in a loaded starting lineup featuring two young stars -- Jaylen Brown and Jayson Tatum -- who blossomed in his absence. In preseason action, Hayward, Brown, and Tatum have been almost indistinguishable in terms of role. They work as secondary options around Kyrie Irving pick-and-rolls, ready to attack a scrambled defense if Irving kicks them the ball.

Hanlen and Hayward worked much of the summer with that situation in mind. They honed Hayward's pump fake so that it would be more convincing, coaxing defenders into flying by him. They drilled slow ball fakes; shoulder fakes; chin fakes; eyebrow fakes.

The first bounce by that defender is the easy part. Hayward and Hanlen focused on the second and third dribbles -- the ones that puncture a defense. Hayward practiced keeping his dribble alive even when help defenders step up to protect the rim. One trick: having Hayward lower his shoulder into that defender's chest, plant his foot, and time his dribble so that the ball and that foot hit the floor at the same time -- meaning he would still have a live bounce after the collision.

Hanlen designed many of those drills so that Hayward planted off his left foot. "He had to trust it again," Hanlen says. Hanlen showed Hayward film of some of the league's shiftiest ball-handlers, including C.J. McCollum.

Having three (and, really, four if you count Al Horford) elite secondary options is great. To win championships, you need to collect so much talent that a few people end up in roles for which they are overqualified.

But Hayward might be the best decision-maker and passer among Boston's perimeter players, and perhaps the best on the team -- neck-and-neck with Horford. As he gets his legs under him, Boston will need to balance the offense so that Hayward gets some time at the controls. That will happen organically as Stevens staggers minutes, giving Hayward a chance to run lineups heavy on bench players. He'll screen for Irving in unconventional pick-and-rolls. If defenses switch, Hayward is ready to drag smaller guys into the post, he says.

The Celtics have time to figure the offense out. Everyone understands the sacrifices involved. "Everyone is going to have games where they score a lot more than they do in others," Stevens says. "I'm not worried about anyone from that standpoint. Everyone will have their chance to shine."

On defense, Hayward will have to jostle with power forwards if Boston is to play its most potent lineups; he defended Kevin Love in the first half against Cleveland on Tuesday. (Brown and Tatum will draw that duty in other matchups, Stevens says.) "He's a strong guy," Stevens says. "He's tough enough." (Beal agrees. After those one-on-one games, he told Hanlen, "'I didn't realize how country strong Gordon is,'" Hanlen recalls.)

Hayward is feeling it all out. He has no doubt he and the team will get there. He just imagines an alternative timeline in which the feeling-out process was further along.

"I wish this could have all happened in the summer," he says. "But I'm working through it now."