Don't think Lopez is going to long relief. 10 of his 15 appearances have been 1 or less innings. Of the other 5, none have been longer than 2 innings. With him throwing 99-100 these days he could be a choice for the high leverage innings that aren't covered by Graveman,Kelly or Foster . Foster has been very good and should be considered a mainstay.
At this point Sousa should be used more than Bummer until the long haul proves otherwise. So right now the top guys in the pen are Hendriks, Graveman,Kelly, Foster Lopez, Ruiz, Sousa. That leaves 1 long relief spot between Velasquez, Keuchel and Bummer. Keuchel could indeed be gone.
But things change so quickly with pitchers with guys getting hit hard or injured. Tough decision but it could become easier between now and the time Lynn finishes his rehab assignment.