Jefferson is a horrible defender. Just awful. That goes against everything this team stands for and has made them successful. Has seeing Mikki Moore and Patrick O'Bryant and watched as great team defense elsewhere went for naught because one big guy couldn't stop anyone from scoring not taught you anything?
Jefferson scores 18 PPG but he gives up 22 PPG. That's a net loss and even though Baby might have his shot blocked a bunch and KG is more of an outside presence and Perk's offense is rudimentary, their offenses are net gains because of the tremendous team defense they play and their versatility on that end of the floor.
This is a terrible analogy - Bryant and Moore have no business being compared to Jefferson. Jefferson should have been an All Star before he hurt his knee. Neither of those guys can put the ball in the bucket.
Next your second paragraph is a great anecdote, but how can you support? Stats? Examples? Observation and analysis? BTW - Perk gives up more of a gap than that against good centers anyways. See for example getting outscored by Howard by double digits. I think his rebounding alone is a defensive asset. How many put backs did we give up to LAL. And the counter example is Ray Allen - a bad defender when he got here, he's shown that in a system where that's valued a guy can transform.
Finally the C's D was fine last year - the problem is their offense sputters out, a guy like Jefferson can keep the O going when teams are forcing Rondo to shoot, and Pierce and Ray are gassed fourth quarter. They could also use a wing that can create, seems that the slashing part of Pierce's game has faded with his increased long range shooting. It hurt us against the LAL because they were rarely in the bonus.
Now I actually don't see him as good fit with JO on board already, but to act like he couldn't bring value to the C's is naive. I think C's need a 6th man SF at this point (please ATL, send over Marvin Williams), but to say anyone who was on a bad team has no business on a winning C's team is to ignore the fact that: KG, Pierce, Allen, Allen, Rondo were all on bad teams. Delonte West was on a bad team, then on a good CLE team - does this mean we can get him or not? It all depends on the overall lineup and team... (Now if you want to make the argument that Jefferson is not a two way player, but is paid like one, I'll agree there - which may be reason enough to avoid him.)