Berrios, 25, is attempting to change the trajectory of his changeup and curveball as complementary pitches to his four-seam fastball -- the most-used pitch in his arsenal.
"Right now, I am focusing on throwing the changeup towards the glove side, which would be on the side outside the right-handed hitter," Berrios explained on a FaceTime call with ESPN. "As it naturally runs for me, it would be on the arm side, from the middle towards the bottom. I want to improve it towards the glove side.
"I'm also working on a curveball, like if I'm facing a right-handed hitter, it goes over the hitter and falls for a strike. I know those are efficient pitches and I want to add them to my repertoire. The changeup comes out in a way that's natural to me, so I want to work it elsewhere."
According to Statcast, Berrios has used four different pitches over the past five seasons: four-seam fastball, two-seam fastball, curveball and changeup.
Between 2015 and 2018, Berríos used his four-seamer 32% of the time, two-seamer 29%, changeup 10% and curveball 29%. Last year, he used the four-seamer and curveball at the same rate, but increased the use of his changeup (16%) at the expense of his two-seamer (23%).
His changeup was remarkably more effective in 2019. Berrios allowed home runs at a much lower rate, and he shaved over 300 points off his opponent OPS. Between 2015 and 2018, Berrios allowed a batting average of .281, .940 OPS and 8.4 HR percentages with his changeup. Last year, those numbers were: .246 BA, .630 OPS and 1.5 HR%.
Oddly, the dramatic adjustment in homers allowed with the changeup happened in a season when the ball flew out of ballparks in record numbers. There were 6,776 home runs in the majors last season, demolishing the previous record of 6,105.
Berrios followed his successful 2018 -- when he went 12-11 with a 3.84 ERA and earned his first All-Star Game bid -- by going 14-8 with a 3.68 ERA last year. He pitched 200 1/3 innings, making him one of just 15 big-leaguers to throw 200 or more innings.
Contrary to many pitchers who have completely stopped their training and bullpen sessions because they don't know when the 2020 season will resume -- or if it will be played at all -- due to the coronavirus pandemic, Berrios has continued working at pace similar to his one during the spring, albeit at a lower intensity.
He's even facing hitters every Friday, including Chicago Cubs All-Star shortstop Javier Baez, his close friend and brother-in-law (their wives are sisters) who lives in the same gated community in Puerto Rico.
"Since I was already at a pace that I would have been for Opening Day, it would not have been to my benefit to drop to a level of 10% or 15%, like in the offseason," Berrios said. "My mindset right now is not that it's offseason. I'm not on vacation. I have tried to follow the plan that I had been doing since spring training.
"I take it step by step, with the tools I have. I don't have all of them, but I am trying to do my best to continue improving as a person and as an athlete. I have to deal with the present situation as it is and keep preparing to return to baseball any time."