Attempting to take an extra base or successfully taking an extra base?
Sorry I can't be definitive. Came in at tail end of discussion and metrics are not my thing. Could have been UBR which, I think, factors in all facets of base running, except SBs/attempts. Kenney was using it, along with defensive outfield metrics, to show two reasons why he would be concerned about picking BH up at too high a cost.