When it comes to 3-point shooting, Celtics have come a long way

The myriad abilities of Al Horford (42) have made the Celtics’ 3-point attack more formidable this season.Barry Chin/Globe Staff/Globe Staff

Last summer, Celtics president of basketball operations Danny Ainge made it clear that one of his primary goals was to add a knockdown shooter. Despite winning 48 games last season, the Celtics ranked 28th in the NBA in 3-point shooting, converting just 33.5 percent of their attempts.

Boston did not acquire a game-changing long-range marksman, though. It signed Al Horford, who became a respectable 3-point shooter last year after hardly ever attempting those shots during the first eight years of his career. And it signed the streaky veteran Gerald Green, whose volume of 3s has essentially replaced the poor-shooting Evan Turner. But those moves did not seem to be enough to ignite a seismic shift.

Now, though, as the season nears its midway point, the Celtics are improbably forging an identity as a high-volume, high-percentage, 3-point-bombing team.

After making 18 of 36 attempts in their 117-108 win over the Pelicans on Saturday night, the Celtics ranked seventh in the NBA with a 36.9 percentage from long range.

“When guys are shooting with confidence and knocking them down, makes and misses are contagious,” point guard Isaiah Thomas said. “When we’re making them, it seems like everybody’s feeling it and doing what they’re supposed to do. We’re at a good place right now.”

The Celtics have made 436 3-pointers, the third-highest mark in the NBA through Saturday. They had even made more than the Golden State Warriors.

So, if personnel shifts were just minor, what has led to this seemingly major change? There are several explanations. First and foremost is the presence of Horford. In addition to the fact that he is a capable 3-point shooter, his skilled passing and ability to space the floor create openings where they might not have existed before.

Now, a player like Thomas can slice into the paint more easily because bigger defenders are drawn away from the basket, and when they inevitably try to collapse on him or another guard, they can fire the ball outside for open 3-pointers.

“We’re playing to our strengths and taking what the defense gives us,” Kelly Olynyk said. “We don’t have a lot of guys to throw the ball in and post up 10, 12, 15 times a game. A lot of movement and a lot of ball screens help us to knock down shots.”

Also, the Celtics have developed some continuity over the past three years, so players have become more familiar with their positioning, and where to find teammates in their preferred spots.

“Probably a little bit of an understanding of where shots are coming from,” coach Brad Stevens said. “So [the shots] may be a little bit better, yeah. And then just continued progress in individual games.”

Of the five returning Celtics who are averaging at least one made 3-pointer per game, Olynyk is the only one who has not improved his percentage since last season.

Getting out the vote

This season fans can help select starters for the NBA All-Star Game by voting for players on Twitter along with the hash tag, #NBAvote. Whenever those tweets are retweeted by another user, that counts as an extra vote.

On Thursday, Thomas received a boost when his hometown team, the Seattle Mariners, vouched for him. That post has been retweeted over 3,100 times. On Friday night, Thomas said that he hoped the Red Sox would do the same. And sure enough, his wish was granted Saturday.

When Thomas was told late Saturday night that the Red Sox had tweeted on his behalf, he smiled.

“Now,” he said, “I just need the Patriots.”

Young ailing

Celtics forward James Young, who has been sidelined since spraining his right ankle during a voluntary workout Jan. 1, said he has been receiving medical treatment twice a day since suffering the injury, but has yet to resume shooting.

“The swelling is going down every day and I’m starting to get some motion back, so that’s a good sign,” he said. “Hopefully in the next week or two I can get in the gym and start shooting again.”

Even prior to the injury, though, Young was no longer a part of the Celtics’ regular rotation. The third-year wing appeared in nine of the first 12 games this season, but has played in just two contests since then.