Lopez fills a role on the team. Every NBA team with playoff aspirations tries to stock a physical 7 foot guy who can spend a couple minutes on the floor. I'd say Lopez is one of the best 3rd string centers in the league, for what that's worth.
Just like how Danny Green's shooting fills a need that the team was missing. Cavs don't need Danny Green to start. Cavs don't need him to guard the most athletic wing of the floor. They just need a small wing that can come in and reliably space the hell out of the floor without being a liability on defense.
Green lets the Cavs put in a killer small lineup of Garland, Mitchell, Green, Love, and Mobley.
Okoro and LeVert have had their moments, but do you feel like you can count on them for a playoff game?