The Boston Celtics fell 104-97 to the Charlotte Hornets in their preseason opener on Friday, as Gordon Hayward and Kyrie Irving took the court together for the first time since last year's disastrous season opener against the Cleveland Cavaliers.

After an excellent first half, during which the Celtics led by 20, Charlotte came storming back in the third when Boston went ice-cold from three. The Celtics' third unit briefly took a fourth-quarter lead, but Miles Bridges' enormous dunks helped the Hornets pull away.

Here are 10 things we learned.

Steven Senne/AP Photo

1. Kyrie Irving really wanted to be back out there.

Irving looked like he was trying to take out some of the frustrations that built up sitting on the bench during Boston's deep playoff run last season. The first basket of the Celtics' preseason was Irving's tough left-handed floater, and he followed it up with a 3-pointer on the next possession -- reminders that when Irving gets going, there really is no way to stop him on the offensive end. In 22 minutes, Irving posted just nine points, but he looked once again like the lynchpin to an excellent offense.

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Kyrie's first bucket of the season 🥳💪 pic.twitter.com/uVUIJztGcC — Kyrie's Handle (@KyriesHandle) September 28, 2018

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Gerry Broome/AP Photo

2. As expected, slowing the Celtics' starters will be difficult.

Boston's offense went really cold in the second and third quarters, but the 37-point first hammered home just how difficult this team will be to handle when they get going. Irving can beat anyone off the dribble. Jayson Tatum destroyed a couple of mismatches when they were presented. Jaylen Brown looks comfortable and confident. Al Horford will be Al Horford. Gordon Hayward looked very rusty, but he was still part of a productive lineup.

Everybody can shoot. Everybody can make plays. They are going to be tough.

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Gerry Broome/AP Images

3. The defense showed mixed results.

We won't linger here long (since, you know, preseason), but you can see why Brad Stevens is concerned about skipping steps. The Celtics had moments where they looked like the switch-happy multi-headed monster that produced the best defense in the NBA last year. They also got beat backdoor multiple times and had plenty of moments of inattention.

We won't read too much into it for now.

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Steven Senne/AP Photo

4. Gordon Hayward looked rusty, but healthy.

Hayward had some ugly misses, which is to be expected. His first shot -- a mid-range jumper -- came up well short and looked like the shot an athlete takes when he still remembers what happened the last time he was on a court.

But he seemed to settle in, and he hit a pull-up 3-pointer out of the pick-and-roll in the second half that will be available to him often this year. His first game back looked like a first game back, but he's building.

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Gordon Hayward's first points this season 😎 #BOSvsCHA pic.twitter.com/nAgpYteiha — Celtics on NBC Sports Boston (@NBCSCeltics) September 28, 2018

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Steven Senne/AP Photo

4a. How did Gordon Hayward grow his hair out so fast?

Gordon Hayward on media day vs. Gordon Hayward ... four days later.

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Hayward's hair grows really fast!

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Charles Krupa/AP Photo

5. The Celtics were absolutely launching 3-pointers.

There seemed to be a clear directive from the Celtics' coaching staff: Every available 3-pointer is to be shot on sight. Shoot first, ask questions never.

So the Celtics launched and launched, finishing with 47 attempts and making just nine of them (a laughable 19.1 percent). It wasn't pretty, but if the Celtics make teams constantly fear they are about to get shelled out of the building, they will find driving and cutting lanes open up more frequently.

Boston's 3-point attempts will be worth watching this year.

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The Celtics shot 13 3-pointers in the first quarter. That's a 52-three pace. That's ... a lot. And they should want a shot profile like that. Everyone can shoot. — Jay King (@ByJayKing) September 29, 2018

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Michael Dwyer/AP Photo

6. Al Horford sat the second half.

Al Horford never came back after halftime, resting as Boston's deep big-man rotation took over. Expect the rest of Boston's stars to get more rest as well as the preseason goes on.

Worth noting: The game tipped Charlotte's way when Horford sat down. Weird how that works.

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Gerry Broome/AP Photo

7. Jaylen Brown showed flashes of an improved handle.

At media day, Brown informed reporters he had been working on his handle during the summer, and he seemed eager to show it off on Friday. Brown looked comfortable and much more in control in transition -- the game looks slower for him with the ball in his hands.

He also did this, which was pretty devastating.

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Gerry Broome/AP Photo

8. Boston had a terrible third quarter (which felt familiar)

If the Celtics are going to launch 3-pointers, they will occasionally go cold, and Charlotte's 39-21 third quarter -- which gave them the edge heading into the fourth -- was a result. The Celtics will keep shaking off rust, but those cold stretches may be an inevitable result of a jumper-happy offense.

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Cody Zeller steps outside for 3 and Gordon Hayward answers! 👌@celtics 71 | @hornets 68 in the 3rd.



📺: @NBATV pic.twitter.com/XW2CvcqOI7 — NBA (@NBA) September 29, 2018

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Gerry Broome/AP Photo

9. Terry Rozier's playoff experience looked evident.

Rozier wasn't always sharp coming off the bench last year, but he looked ready on Friday. How he adjusts to moving back into that role will be important, but he certainly looks better prepared to attack second units now.

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Steven Senne/AP Photo

10. Robert Williams looked a little nervous, but really energetic.

Williams entered the game in the third quarter and rifled a pair of passes so fast, they nearly broke fingers. He settled down a bit after that and showed some nice instincts offensively as a pick-and-roll big man. He didn't look certain where he was supposed to be defensively, which is to be expected, but there's no denying his enthusiasm, or his incredible physical tools.

There's a lot to work with in the young big man, and per Celtics sources, he was a dream to work with all summer.

Encouraging signs abound for the Celtics, even after a loss.

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