Bummer's biceps muscle has healed, but he's now dealing with a nerve issue near the biceps, Scott Merkin of MLB.com reports.
White Sox general manager Rick Hahn explained that this is not a long-term issue but acknowledged the possibility that Bummer may not return in the shortened 2020 season. "It really comes down to getting that nerve calmed down and then as we ramp him up, which we have started to do on a throwing program, how the nerve responds. It's quite possible, based on how the throwing program lays out, that you see us at some point put him on the 45-day IL," said Hahn. With Bummer sidelined, Evan Marshall has picked up a majority of the setup work in front of closer Alex Colome.