When the Celtics agreed to sign Gordon Hayward to a max contract last summer, they knew they would have to make a trade to free up the necessary salary-cap space. They acquired Marcus Morris from the Pistons for Avery Bradley because they liked his versatility, his shooting, and his toughness. But when Morris arrived in Boston for the first time last September, Celtics coach Brad Stevens met with him and made another reason for the team’s interest quite clear.

“When I first got here, I wasn’t sure why, or where I was going to fit,’’ Morris said. “And Brad sat me down and said, ‘We brought you here to be able to defend LeBron [James] when we get to the Eastern Conference finals.’ And we’re here now.

“I’d say it’s a little amazing to know that this situation was going to happen back in September. For them to be able to see this far, and it to come out to play how it is, it’s a little amazing. So I’m here to fulfill the dream.’’

As the Celtics prepared for Game 1 of the Eastern Conference finals over the past few days, they went to great lengths to emphasize that defending James is no one-man job. Even Stevens, the man who told Morris that he had been brought here, in part, for this moment, quickly deflected a question about Morris’s role in the series.

“Totally a collective effort,’’ he said of defending James. “Totally a collective effort.’’

It is probably partly because it will be a collective effort, and partly because there is no sense prodding James about a specific matchup. But the challenge of defending him has to start somewhere, and make no mistake, it will start with Morris.

The forward sat out one of Boston’s three games against the Cavaliers this season, but guarded James for a total of 55 possessions during his 50 minutes vs. Cleveland. James was successful, making 8 of 16 shots, drawing four shooting fouls, and scoring 24 points.

Jaylen Brown has been Boston’s No. 2 option against James, and he will be called upon quite often in this series, too, especially since Morris comes off the bench. Over 100 total minutes against Cleveland, Brown defended James for 57 possessions, and James made 8 of 15 shots and scored 19 points, but Brown did not commit a shooting foul.

The third most likely option will be rookie forward Semi Ojeleye, whose confidence soared after a successful run defending Bucks start Giannis Antetokounmpo in the opening round of these playoffs. Ojeleye, who is likely the strongest of the three, may actually have made it the most difficult for James to find open shots. In 39 possessions against Ojeleye, James scored just 6 points on 3-of-6 shooting.

After those three players, the dip is significant. Jayson Tatum and Marcus Smart defended James for 12 possessions apiece during the regular season, and James mostly feasted, going 4 for 5 against Tatum and 3 for 4 against Smart.

Brown defended James often during last season’s conference finals, but Morris has the most experience against him overall. He guarded James throughout the Pistons’ first-round playoff matchup against the Cavaliers two seasons ago, and he said that experience taught him that he needed more preparation to tackle this unusual challenge.

“I’ve matured,’’ Morris said. “I obviously got stronger, got smarter as far as watching film. Back then I wasn’t really watching film. Now I’m a student of the game and watching tendencies and watching other players defend him well. I’ve been trying to see the success other defenders had against him and trying to use that and integrate that in what I do.’’

Morris said he studied Spurs forward Kawhi Leonard’s approach to defending James most of all. He said that Leonard is unusually active with his hands, and that it seemed to be effective. He also said that Leonard does a nice job of mixing up his coverage, such as sometimes going under screens and sometimes going over them.

Morris also admired Pacers guard Lance Stephenson’s approach to guarding James, both in the past and in the first round of these playoffs. Morris said Stephenson is a physical presence who constantly reminds James he is there, whether he is bumping him away from the ball or picking him up in full-court situations. In the end, though, Morris knows he will need to stick with whatever works best for him.

“Coming into this year, once I got traded, this was on my mind,’’ Morris said. “So I really worked to get stronger. I’ve been working toward this point for a long time to just challenge myself and see where I’m at guarding one of the best players. He’s going to get everything I got.’’

James played a total of 102 minutes against the Celtics over three regular-season games this year, and although it is a small sample size, it does provide clues about the areas in which he might be most effective in this series.

The Cavaliers outscored the Celtics by 8.9 points per 100 possessions when James was on the floor, and he will be on the floor more often now. He is averaging 41.4 minutes per game in the playoffs compared with 36.9 during the regular season.

The Celtics generally did well to keep James off of the foul line, as he attempted just 6.5 free throws per 100 possessions, his sixth-lowest rate against any team. He also made just 25 percent of his 3-pointers, and make no mistake, the Celtics would rather have James firing away from beyond the arc than carving through their defense to either score or find easy opportunities for others.

Interestingly, James’s greatest impact against the Celtics came on defense. The Cavaliers’ 109.5 defensive rating ranked 29th in the NBA. But with James on the court against Boston, Cleveland’s defensive rating was an elite 97.5, more than 4 points better than the Celtics’ league-leading 101.6 mark.

James pulled down 14.5 rebounds per 100 possessions, his second-highest mark against a single team, and the Celtics registered just 6.5 second-chance points per 100 possessions when James is on the court, the fewest of any of his opponents.

In addition to finding ways to stop James, the Celtics will need to find ways to make him exert energy when they are on offense.

James guarded Brown for 89 possessions — nearly twice as many as Brown guarded him — and he had great success, holding Brown to 2 for 21 shooting.

But Brown said it will be important to ensure that James is challenged on defense in this series.

“He’d better be alert, because if he’s not, I’m going to get it going,’’ Brown said.

“You’ve got to make him work on both sides of the ball. Usually he’s guarding the least-offensive threat on the floor, so if he’s guarding me, I’m going to make him pay.’’

Adam Himmelsbach can be reached at adam.himmelsbach@globe.com. Follow him on Twitter @adamhimmelsbach.