Morris. Judging by the sample size we have at this point (throw out the Sac anomaly) the losses have been to the LA teams (with LeBron & Kawhi). If the Jamzz want to win it all this year, gotta find an answer for those two.
Rebounding is an effort stat, that's why Westbrook @ 6'3" averages double digits. Rodman (likely 6'6"ish) averaged 18 because he was focused on that. Even Barkley (6'4") outrebounded taller opposition. If O'neale and whomever else is in the PF spot focuses likewise, it won't be as necessary as what Morris can bring the team.
Still, the Lakers worry me the most in a seven game series. Aside from LBJ, they have four big guys to throw at Rudy - AD, Cousins, Dwight, and McGee. They're going to be tough to crash the boards against. Hopefully DeMarcus loads all their bigs up on purple drank... wait, that was JaMarcus...
For some reason the Clippers don't concern me too much even without a defender for Leonard.