As we expected, Craig Kimbrel signed after the MLB draft, now that he is not connected to draft pick compensation. You could argue this was the best possible destination for Kimbrel as the Cubs have generated a lot of save chances to this point. He needs to be owned in all leagues, though you may not get your first save from him until July.
In a saves+holds league, I think Steve Cishek and Pedro Strop are still ownable. In fact, Pedro Strop should be owned in all leagues until Kimbrel returns. Strop returned from the IL Tuesday and pitched a scoreless inning to pick up his fifth save of the season.