Smith worked on his curveball during the offseason, Steve Gilbert of MLB.com reports.
Because Smith feels his slider is too similar in speed to his fastball, the left-hander wants a slower breaking ball. It was a pitch he introduced last season, but a bout with COVID-19 last summer limited him to just 14 innings. He never got a chance to develop it fully, although he did throw it 20 times and did not give up a hit on it, per Statcast. "The curveball is coming along really well," Smith said. "I picked it up pretty quick, actually. I think it's right where I need it to be. I think it's going to help my repertoire a lot this season." Smith is expected to be part of the Diamondbacks' rotation in 2021.