When he was acquired from Detroit last year, Jonas Jerebko was able to make an immediate impact for the Celtics. His high-level distance shooting, tenacious rebounding, high-effort defense, and extensive versatility allowed him to work his way into the Boston rotation. He played a crucial role to the team's success throughout their end-of-season stretch of unexpected success.
Because the team has so many capable rotation players on its roster, every Celtics player is in some danger of having his minutes cut this year. This is particularly true at the power forward position (even if Brad Stevens doesn't necessarily think it exists), which is where Jonas earned much of his time last season.
Coach Stevens took the opportunity to respond to this line of thinking at the Celtics Media Day.
It is essential to look at the roster through Brad Stevens' eyes when trying to understand what he is doing with the team. Much like his view on positions (he only believes there are 4 of them), this is another example of the brilliant young coach looking at things through a slightly different lens than most of the rest of us. Instead of deciding what role a player will fill on the roster, Steven's determines what it is that they're good at, and then determines when those skills will be best put to use on the court.
There are certainly some skill sets that work in almost all situations, and against almost all opponents - Marcus Smart and Avery Bradley's aggressive and stifling perimeter defense and Isaiah Thomas's ability to score and distribute out of the pick and roll are both examples of skills that work against almost every opponent.
Jerebko is a multi-faceted swing who can strike from distance, defend both forward positions, and get after offensive rebounds. There is no other player on the team who meets all of those qualifications (we haven't seen Crowder shoot well enough to list him as a true comparison). As such, he will likely see the floor when we are going up against strong combo forwards and small-ball lineups, and when we have IT on the floor as a drive-and-kick distributor.
This is probably the way that we'll have to look at playing time for players moving forward. Because we have such a deep team, and because we have such a selfless offensive style, playing time will likely be largely based on when a player's role is necessary, when looking at the situation and the opponent. The players on the Boston roster have consistently displayed a 'next man up' mentality when asked about playing time, indicating that every player could be called upon, depending on circumstance. We would likely all save ourselves a headache by adopting the same view when analyzing playing time as fans.
As to the question of how many minutes Jerebko will get, we will have to base our answer on the intelligence of Boston's coach, and assume that it'll probably be exactly as much as the team needs from him.