"Someone" is probably going to be Nola though. You won't leave him off the roster but it's possible he never pitches in the NLDS. Walker neither. Whether because they don't need him or because it's a long series and the "4th" starter is actually the Game 1 NLCS starter.
I would expect we will see Duran enter a game with men on or pitch multiple innings if he has to. Everything change in October.
If Nola does end up as one of three starting pitchers, then sure, maybe Luzardo doesn't throw a pitch in that series a third LH reliever isn't called for. But he could also just be scripted to come in right after Nola.
All of Luzardo's flaws as a reliever still apply to him as a starter. Either way, Ranger is our second-best starting pitcher.
Not sure about Kerkering being good with inherited runners. What is it, 14 out of 30? But he's been asked to do it a lot.