I wouldn't be surprised if his last couple of injuries have meant he's had to alter his running technique a bit. Tom Turbo and Trell Mitchell have had to do something similar in recent years and it took time for them to get back to their best.
Plus, Newman hasn't exactly had much quality ball on a dry pitch, so it's exactly going to showcase his talent. We could also still be limiting his workload to ease him back in, which is wise if it reduces his risk of injury in the future