JB is right - don't use a waiver pick on them. Valverde may be worth a FA pickup, depending on who you'd drop. He won't get any saves until Mantei gets injured or traded. Long term, Valverde is the best value.
Riske may be a better bet for getting saves. He's probably the best FA pick right now. If Wickman can't hack it during ST then Riske will be the Indians closer. Again, not worth a waiver pickup, but I'd try and get him on the roster.
Lidge will not close this year unless Dotel blows it. That is unlikely to happen. Dotel should excel as closer. That doesn't mean Lidge isn't worth having on your team - check out Dotel's numbers from the last few years. Solid MRs who get decent IP can be really helpful on a roto team. Less so on H2H squads.
"The game has a cleanness. If you do a good job, the numbers say so. You don't have to ask anyone or play politics. You don't have to wait for the reviews." - Sandy Koufax