WALTHAM — Al Horford showed up early to the Celtics facility, well before yesterday’s official start of practice, and began looking for any sign of improvement in the group his former Atlanta Hawks team routed in the playoffs last spring.

One day during a 5-on-5 scrimmage, the new C’s center saw a couple of bombs drop from the corner.

“Jae Crowder came in and played with us one day, and his 3-point shot has gotten better,” Horford said.

And Horford’s most recent memory of Crowder, before that informal scrimmage, was of an injured player at half speed, attempting to shoot 3-pointers and defend on a high-right-ankle sprain as his team made its second straight first-round exit.

“We knew he wasn’t healthy, there’s no question about it,” Horford said. “But he’s healthy now, and we’re happy. It’s a good thing. (Crowder’s jumper) just seems more fluid. He seems more confident in it. When the season gets going, we’ll see.”

Crowder’s ankle twinges with pain just at the memory. He shot 24.4 percent from downtown during six playoff games after shooting 33.6 percent in 73 regular-season games.

The process of shooting an NBA-length 3-pointer is difficult enough without trying to launch those deep shots on a bum ankle.

“Very difficult. I didn’t even know it was that difficult because you need everything,” Crowder said. “I was shooting a couple off the dribble coming off a pick-and-roll, and I was shooting a few spot-up shots, but I just didn’t have the lift I needed to make shots consistently.”

But nothing, perhaps, suffered more than his defense. Crowder, who can normally switch where needed, was isolated twice on Hawks point guard Jeff Teague late in Game 1, and he was turned for an easy layup each time.

“Ah, he went right past me,” Crowder said. “I’m able to switch, but I just couldn’t push off the way I wanted to, I just couldn’t do the things I usually do. That’s the play that stood out to me when it was all over.”

And those are the plays that drove him back to the Boston area two weeks ago. High-ankle sprains take the longest to heal, and as a result, beyond an intense schedule of pool workouts, Crowder spent the first two months of the offseason clearing his mind.

“But I was thinking how we played that whole series in Atlanta, and I was physically beat up,” he said. “I just wanted to find a way to get my body better. It was a freak accident, an ankle injury that I couldn’t prevent. (The offseason) cleared my head a little bit, but I still thought of it a lot. The pool was where I started. I needed to figure out a way to stay in condition while I wasn’t on the court. I converted to a pool workout. By June, I was in the pool.”

That was Crowder’s price for choosing to play through a debilitating injury.

“I was not close to 100 percent, but I felt like I couldn’t sit out,” he said. “I couldn’t take any day off because at that time, we had to be all hands on deck. I just tried to suck it up as much as possible. It limited me a lot, but I just felt like my spirit just being out there with the guys and fighting was more than me just taking that game off or that series off, or sitting out anything like that. I just had to get out there.

“It’s unfortunate that the injury happened, that late in the year, and I thought I was ready to go and bounce back. But I was more fatigued, my ankle was more fatigued than I really realized. Right now, I’m healthy. The way the season ended really gave me a chip on my shoulder to get better and to get in the lab and work and get better at the things I need to work on. I think everything happens for a reason.”

Motivation is probably a good part of that reason.

“That’s what it is — it’s motivation,” Crowder said. “I had had a great year up until the injury, and I just wanted to have a complete season. I feel like if I was healthy, we could have done more in the playoffs, but I have to live with that. But it did drive me a lot this summer.”