If one looks at that chart, he stopped using the 2-seamer as much in 2017. Maybe not coincidentally 2017 was his first good year when he established himself as at least a number two starter.
Bkox may be right that hitters are sitting on the 4-seamer too much but I don't think it is at the expense of the 2-seamer. I am guessing he is just missing locations with all pitches more. So his curve is less effective when used. When he needs a strike he goes with the 4-seamer too much.
I think it is possible expectations with Nola were just too high. He is a very good pitcher, but he does not have dominant stuff. He also might lose an edge with a heavy workload because he is not that big a guy. Simply put, he is a number two and not a number one. That is not a putdown against Nola. His stuff is more like a number three and he made himself better than that, especially by showing that durability. Big guys that sit 96 just last longer and are more dominant than smaller guys that sit 92-93 like Nola. More margin for error and more durability over long periods of time.
