Al Horford breaks down Boston's mindset heading into the season and reveals what he learned about the team last postseason. (1:36)

CANTON, Mass. -- Last summer, new Boston Celtics arrivals Kyrie Irving and Gordon Hayward beamed just imagining what it would be like to share the court together.

Those dreams lasted all of five minutes before Hayward was lost for the season to a gruesome leg injury on opening night.

The Celtics somehow survived it and had set themselves up to make a run at the Eastern Conference title when Irving was lost for the final stretch of the regular season and the playoffs following a pair of knee surgeries.

But four months after a season with so much potential was tossed into the "what might have been" basket and following an offseason conference shake-up that saw LeBron James head west to Los Angeles, Boston again finds itself in the spotlight heading into training camp.

Irving and Hayward are back and healthy. And they are flanked by a loaded roster of veterans and talented young players who are hungry for another shot at the franchise's 18th championship.

Irving said last season taught him not to take anything for granted.

"I missed it so much, and for it to be taken away the way it did, with the timing and everything, it just wasn't ideal," Irving said Monday. "It was hurtful, honestly, because it was an uncontrollable thing. To go through it was a learning experience, but it only helped my evolution as a person."

Gordon Hayward, left, and Kyrie Irving are back for the Celtics and healthy. Brian Babineau/NBAE via Getty Images

Hayward, who is playing without restrictions following a more than 10-month rehab process, played 5-on-5 earlier this month for the first time since his injury.

He said going through the preseason will help him feel 100 percent healthy.

"When you don't play basketball for a year, those things happen. I have to find my rhythm, find my groove a little bit," Hayward said.

Though he feels like a newcomer to this team in some ways, he said he doesn't feel any pressure.

"I don't think I necessarily have anything to prove," he said. "But internally I want to be the best version of myself."

If there was one positive thing that resulted from the absence of Irving and Hayward late last season, it was the emergence of second-year Jaylen Brown and rookie Jayson Tatum.

Thrust into starting roles late in the season, both emerged as members of the NBA's next generation of All-Star-caliber players.

Brown proved the athleticism and defensive ability he showed in his first season were no fluke. And Tatum, just 19 when the season started, played fearlessly in the postseason, averaging 18.5 points per game.

What was once thought to be Boston's new Big Three of Irving, Hayward and Al Horford has quickly been recast as a Big Five.

It's left coach Brad Stevens with the enviable but delicate challenge of getting the projecting starting five of Irving, Hayward, Horford, Brown and Tatum to jell while also integrating a talented bench that includes Terry Rozier, Marcus Smart, Marcus Morris, Aron Baynes and Daniel Theis.

Rozier made the most of starter minutes when Irving was sidelined, and Smart and Morris were defensive cogs on a team that pushed the Cavaliers to seven games in the conference finals.

"We have a long way to go. That being said, we clearly have a lot of good players," Stevens said.

Morris said the first task for this group will be leaving the egos in the locker room.

"A blind person can see that we have a lot of talent," Morris said. "So obviously we all know that there is some type of sacrifice that we have to take for the betterment of this team."

Figuring out how to use the talent they have will be the fun part, Tatum said.

"Everybody's gonna have a different role, just with the loaded roster that we have," he said. "Whatever it takes to win. That's what we care about. Winning takes care of everything."