If the Kings have one of the worst 5 records in the league at the time, McLemore looks like a legitimate prospect, they throw in Fredette or Thomas, and they take on one of our veteran contracts (Lee, Bass, Wallace), then I say yes.
He's talking about a draft day trade. Do it during the season and you're screwed. The Kings would immediately get better with Rondo, they'd have no incentive to lose games (to better another team's pick) when others around them are tanking and the difference between 5th and out of the top 10 would only be a few wins.
Eh, if the Kings have a bottom five record at the trade deadline I don't think they're gonna make up a lot of ground half-way through. I don't think adding Rondo to that team suddenly makes them a 50 win caliber team or anything. At most it'd give them an extra 4-5 victories. Maybe that's the difference between a top 5 pick and being out of the top 10. I doubt it, though. Last year, the difference between 20 wins and 25 wins was only a couple spots. The difference between 25 wins and 30 wins was a handful of spots.
So sure, ideally it's a draft day trade. But I'd be fine with trading Rondo to the Kings if they're sitting on a sub .300 winning percentage at that point and McLemore looks like a really good prospect.
The thing to remember is that if the Celtics trade Rondo halfway through the season rather than on draft day, it means their own pick is probably that much higher. That would off-set whatever effect Rondo might have on the Kings' record.
I don't think "we'll be worse without him" is much of a justification for making a trade for Rondo that isn't likely to net a comparable player in return. That's the right move if you're Seattle looking to unload a player (Ray) that's 4-5 years older than Rondo, not when you have a player who's 27 or so.
Well, obviously "we'll be worse without him" is not the only factor at play. It just means that your concern about making the Kings better by sending Rondo to Sacramento halfway through the season would be off-set by the likely improvement in the Celtics' pick -- in a sense, the Celtics would just be switching spots with the Kings, but they'd have two picks instead of one.
On top of that, in this scenario they'd have a prospect with a high ceiling at a position that's rather lacking in talent around the league these days.
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The Seattle example is an intriguing one. Honestly, I don't see that the Seattle situation was really that different. Sure, Ray was a few years older then than Rondo is now. But Ray was also much better in his prime than Rondo has ever been (surely you can agree with that), so he had farther to fall. Also, he had a game that was likely to age really well, despite his ankle issues. Here we are 7-8 years later and Ray is still a quality shooting guard. Back then, he was one of the best at his position in the league.
Rondo is also one of the best at his position in the league, though not among the very best -- even when he's healthy. Considering his strengths and weaknesses, he probably has another 5-8 years of high quality play left in him, assuming a full recovery from his knee injury and relative health after that.
Meanwhile, the team around him is pretty much devoid of talent. Indeed, there's less talent on the Celtics right now than there was on that Seattle team, since they were about to get Durant in the draft. But they traded Ray for a package of young assets, and they hoped one of those would turn out to be more valuable over time.
As it turns out, Ray has been the more valuable player by far the entire time that Green has been in the league. Still, trading Ray for those assets made it easier for the Thunder to bottom out, which helped them get Westbrook and Harden. Both of those guys have been much more valuable than Ray the entire time they've been in the league.
While Green didn't end up being part of their star core, he was nonetheless a valuable trade asset that gave them the ability to make moves to try to win a title. Trading for Perkins, as it turns out, helped them get to the Finals.