The Cs made it to Game 7 of the Conference Finals without a suitable backup to SF Paul Pierce, but they won't be able to squeak by again this year. Pierce sprained his MCL and looked gassed in the playoffs against elite wings like longtime rival Lebron James.
The Cs require someone off the bench with the athleticism to defend the league's best scorers, who are almost invariably swingmen.
Boston needs an ace in that role. With Green, they've got a wild card.
Though he's entering his fifth full season in the NBA, Green is still very much a prospect. He's only 26 and already he's shown flashes of the player he's capable of becoming. But he's also fresh off a season lost to heart surgery, which itself was preceded by a half-season of middling play for Boston.
Green enjoyed three straight seasons with the Oklahoma City Thunder in which he averaged around 15 points and six rebounds. He's got freakish athleticism, and conventional wisdom dictates that he's a candidate to see his numbers increase sharply with transition buckets set up by PG Rajon Rondo.
There's a strong argument against Jeff Green's rate stats rising steeply as part of an up-tempo bench, laid out in a comprehensive article on Celticstown.com. Basically, the author argues that Green was below league average in Player Efficiency Rating (PER) during his 2010 season with the Thunder, who were 12th in the league in pace (possessions per game), so running with the Cs won't do much for him.
But what the author doesn't take into account is that Green will likely share plenty of floor time with Rondo, last season's NBA assist leader. There's a huge difference between running in transition with a guy who's looking to pass first (and set up his teammates in optimal spots) and running with a scorer.
Green's point guard in OKC was Russell Westbrook, a star in his own right but one who can generously be described as a shoot-first guard. Westbrook racked up more PPG than any other point guard last season.
When you've got a player like that at the point, he's primarily looking for his scoring opportunity. That means that by the time he does end up passing it on the break, the defense often has time to recover against the other guys in transition.
That, plus the fact that Green was part of a starting lineup that also featured the NBA's best scorer in Kevin Durant, meant that he wasn't close to the primary option in most of the Thunder's offensive sets and transition plays.
So look for Green to run with the second unit plus Rondo, and watch his efficiency increase dramatically as he's afforded easier transition buckets.
On defense? That's a bigger question.
Green looked lost in the Cs defensive rotations during his first stint with Boston in 2011. He has the pure athleticism to stay in front of the elite wings, but the Celtics defense isn't predicated on winning one-on-one matchups.
He'll need to pick up the rotations and play good help D to crack the rotation. That's especially true if he hopes to contribute against the defending champion Miami Heat, who boast two of the best wings in the league in Dwyane Wade and Lebron.
Hopefully, a full training camp with the Cs will allow Green the chance to pick up Coach Doc Rivers' complex scheme.
If he does, he'll see time at both forward positions. He's a liability on defense at the 4, allowing a 20.5 PER as a PF in OKC's system (per Celticstown.com). In other words, he allowed the PFs he guarded to play like 2011-12 Pau Gasol, on average.
Green will add depth to that position, but he's not an ideal option there.
Where he'll make his most important contributions, as I've mentioned, is at the small forward position. Paul Pierce can't guard Lebron or Kobe Bryant all night and still chip in offensively anymore. The "Truth" broke down in the playoffs, and his subpar performance in the Eastern Conference Finals may have cost them a Finals berth.
Thus, more than anything else, the Cs need Green to step up defensively so they can keep Pierce fresh and healthy. Green is the key to their depth, their bench and their flexibility.
In fact, as the highest-ceiling member of a stacked Celtics bench, he's the key to their title hopes.
That's a lot of pressure to place on a 26-year old coming off an aortic aneurysm.
But the Cs know what Green is capable of, and they expect him to fulfill the incredible potential he's flashed in the past several seasons.