Sometimes players just doesn't workout in certain cities under certain coaches/organizations because the schemes don't fit the player or the atmosphere & players around the player doesn't fit cohesively.
I'd say Jimmer Fredette is a bad fit for Boston under Brad Stevens because of his defensive deficiencies. MarShon Brooks didn't play much for the Celtics. I don't think the Celtics will be acquiring scorers who can't defend.
MarShon Brooks didn't play because he wasn't in the future plans, and he had no real trade value around the league. If Jimmer is brought in, I'd assume the Celtics at least have the option to bring him back next year, if it isn't guaranteed in the contract. Once you know a guy may or will be around, it makes a lot more sense to play him despite his deficiencies.
MarShon Brooks and Jimmer Fredette are both the type of player who shouldn't be in the team's future plans.
Convince me that Fredette can be a better defender than Eddie House and I might change my mind about him.
Who cares if he's a better defender? We're 26th in Offensive Rating this year and 28th in 3-point shooting. Our defense is 15th -- while that's not championship defense, it's not what's holding us back.
You can't build a team around 15 complete players -- those players cost too much money. You need some cheap specialists who compliment each other to go around 2-3 expensive, complete players. If you can get a specialist like Jimmer, who's bordering on elite when it comes to perimeter scoring, for a bargain that doesn't cost you anything other than an already empty roster spot and the money you have left under the luxury tax line, you do it, and you try to lock him up for a few years. At some point in the next 3-4 seasons, the Celtics will hopefully be back in contention, and then they'll be scrambling around to get a backcourt scorer, costing themselves a couple of 2nd round picks. Might as well take care of the problem now and save the picks for some other need (probably the always needed veteran post presence).
If we don't get him, we don't get him, and life moves on. But I think the Celtics, at least the current version, would be better off with him than without. He can have Bayless' minutes, please and thank you.