PU'S defense will be much worse without the rim protector and Davis the stopper. IU has Josh Newkirk who transferred from Pitt and is sitting out for an experienced point guard. Haas is horrible on defense. He can't defend screen role. A lot of improvement is needed there.
I won't comment on IU's situation, but I will give you my take on 2017 Purdue Team. Even as he is now, Haas changes opponent's shots. Hammons waits for the shot to go up and then blocks. Haas stands with his hands over the shooter, and stops the shot, forcing either a circus type maneuver, or a pass back out of the paint. He will never have the block numbers Hammons has, but he is just as effective in the paint defensively. We may miss Hammons offense more than his defense.
As for replacing Ray Davis, I think we will be okay from a physical perspective. Smotherman is an excellent high-energy defender. He may be better at defending stretch 4's and tall 3's than Ray Day. Ray was often assigned taller players, and he did okay by pure hustle. Smotherman brings that same hustle. It is Ray's off-court leadership we will miss. I hope others step up. Swanigan, Mathias, and Cline all have potential leadership in their DNA.
As for defending opponents' guards, that will be done by committee. Mathias, Stevens, and Cline will be okay, but not as good as Davis. The offset is that all 3 will be more of a scoring threat than Ray. The idea is to score more points than the opponent, which can be done through either better defense or better offense. Remember, Ray Day came into his own his Junior year. Mathias and Edwards will be juniors next year.
I don't expect much impact from the 2016 class. Carson will be an important addition, but the 2017 class will be the hallmark for Purdue and not the 2016 class.