Forgive my dramatic intro, but I really don't think you can understate the impact that this will have on the team. When a team's best player misses half the season and then returns, that's big. When he happens to play point guard, that's huge. When you are in a rebuilding mode and everything is (in theory) geared toward building around that star... well, like I said, it changes everything.
First a caveat: I'm talking about mostly-full-speed-Rondo. Who knows if he'll be on a minutes restriction or if he'll still be struggling with confidence in the knee or whatever. I don't know when he'll be BACK but at some point (maybe in his first game, maybe not till next year) he'll have a game where you just know that the old Rondo is running the show again.
So let's look at all the ways that Rondo could impact the Celtics this year:
1. Depth Chart
We'll finally have a legit point guard again. Some have filled in admirably for a time but extended playing time out of position is never the best thing for the team or that player. Rondo starts at point guard and presumably Avery Bradley stays at shooting guard next to him (more on him later). Crawford heads to the bench where he'll split time with Jared Bayless backing up both positions. Theoretically Stevens can ride the hot hand since both are streaky players. Pressy probably sees his minutes cut the most out of the group.
Wildcard: MarShon Brooks, as little as he's been used, might still have some small glimmer of hope to squeeze his way into the lineup. On the surface it doesn't make sense since there will be fewer minutes to go around. But again, everything changes with Rondo in the mix. If he somehow clicks with Brooks, he might finally get a chance to prove himself.
2. Changing Roles
Who's the leader of this team? We've been asking that since training camp and the only answers we've come up with consistently are Brad Stevens and Rajon Rondo (from the sideline). Jeff Green has been a focal point when he hasn't faded into the corn like Field of Dreams. Jared Sullinger has stepped up his game but is probably still a little young for that role. Gerald Wallace talks a big talk and walks a small, ineffective walk (sorry Crash). Now we'll have an unquestioned alpha dog who finally has a team to call all his own.
Brad Stevens has tried to tailor the offense to Rondo's strengths, which is an extremely hard thing to do when the key piece is missing. It won't likely be the "pound the ball into the floor waiting for Ray Allen to curl around 4 screens" offense we saw for years under Doc Rivers. Rondo may have to move without the ball more than he has in a long time. With that said, he's still going to see things others don't or can't see. Plus, when the clock is winding down, the ball will be in Rondo's hands and not Jordan Crawford's. That alone has to count for something.
3. The Jason Kidd / Steve Nash effect
Whenever Jason Kidd or Steve Nash changed teams (during their primes) a funny thing happened. All the average players on their new teams got better. Sometimes they signed big contracts to go play elsewhere and subsequently fell flat on their faces. Having a great point guard just has a way of making everything work better.
We've got some young guys still learning the ropes and some guys that may have hit a plateau in their careers. If anyone in the league could give each of these guys a boost in the right direction it is Rajon Rondo. He might get Jeff Green 3 or 4 more looks in the open court per game. He'll find Bass for his sweet spot elbow jumper right where he likes it. Kelly Olynyk will be on the balls of his feet with hands poised because he knows if he's open he'll actually get the ball.
Avery Bradley might be impacted the most. Right now he's leading the team in shot attempts. He's become a default go-to guy because he's got the confidence to shoot and he's one of the more talented players on the team. That's great, but I can't help but feel like Rondo can put him in better positions to score. Also, with some of the offensive load relieved, he can put some more emphasis on his superpower - namely defense.
4. Prime Time
This current version of the team is fun to watch from a certain perspective. They (usually) work hard, they are growing, and you never know what's going to happen next. With that said, unless they are in the process of upsetting a much better team (Miami for example), they aren't exactly SportsCenter material. Sure there's the occasional Jeff Green dunk on the top 10 and the occasional Kris Humphries getting dunked on. But there's not a lot of swag on this team.
Rondo changes that for the better. He makes this team interesting from a national standpoint again. I know that isn't necessarily important to diehards like you and me, but it might matter to the players. What quality free agent is signing with the Celtics this offseason if Rondo isn't part of the long term plan? They still might not sign in Boston anyway, but Rondo at least gives them reason to ponder it.
I'm sure I've missed several other impacts that Rondo will have on the team, for better or worse. Chances are good that his return could have some negative impacts on some players. Will Jordan Crawford fall right out of the rotation? Will players struggle with the fact that they won't be touching the ball as often? Will Rondo flat out flip out when he sees something that the guys on the court simply don't get?
I have a lot more faith in Rondo's maturity and patience than many talking heads and national writers. But even I have to admit that you never know with Rondo. He's always going to have a fire and an edge that makes him who he is - both in a positive and a negative way. Maybe Stevens is just the kind of calming influence he needs but you can't count on that 100%.
But flipping that script, you never know who might just be on the same wavelength as Rondo. Maybe when Jeff Green starts to fade into the background, Rondo will see that and grab him by the ear and forcefeed him the ball. Maybe when Crawford is doing bad-Steez things Rondo will work the ball into Sullinger instead. Rondo really is on the level of an assistant coach out on the court and there's no telling what he'll see (on a micro or macro level) that none of us could have expected.
So yeah, you could say that Rondo will have a big impact on the Celtics.