The money will determine what we should really think of this deal, but I see two general outcomes.
1) This is a fine deal that doesn't much move the needle. Rose's three point shooting reverts to normal (for him) and he fits into our system almost exactly as Reggie does. He comes off the bench, provides adequate shot creation and adequate passing that the team desperately needs more of. But, his continuously poor defense will make what he brings a wash, and the team will be about the same as it was with Ish.
2) This becomes a really good deal because Rose's shooting continues and he ups his volume. It opens up the spacing we desperately need. He is still the primary backup, but also finds value playing alongside Reggie in offense-oriented lineups. The team improves by 5 wins simply from greater consistency on offense (both better overall shooting and less bouts of stagnation).
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I think 1 is far more likely than 2, but I don't see how this could really be bad unless the money is exorbitant. As long as we are paying for the player Rose IS, and not the player he once was, it should be fine.