The Philadelphia Phillies happened upon Sánchez when they saw him throwing batting practice at a workout for a Cuban catcher the Phillies were scouting in 2014. He signed with the Phillies for a $35,000 signing bonus as an international free agent in February 2015. He made his professional debut as a pitcher that year with the Dominican Summer League Phillies. He had 1–2 win-loss record with a 4.56 earned run average. He pitched in 2016 with the Rookie Gulf Coast Phillies. He was 5–0 with an 0.50 ERA, a WHIP of 0.759, and a 5.50 strikeout-to-walk ratio. At 17 yearsof age, his fastball was 97-98 mph. He was named both a Baseball America Rookie All Star, and a Gulf Coast League Post-Season All Star. Baseball America named him the Number 80 prospect in baseball. Sánchez started 2017 with the Class ALakewood BlueClaws, and was promoted to the Class A+ Clearwater Threshers during the season, with whom he was the youngest pitcher in the Florida State League. On July 30 he was named Southern League Pitcher of the Week. He threw a fastball in the high 90s that reached 102 mph. Between the two teams he was 5–7 with a 3.03 ERA, a WHIP of 0.958, and a 4.67 strikeout-to-walk ratio. Baseball America named him the Number 25 prospect in baseball, MLB.com ranked him as the Number 26 prospect, and MLB Pipeline named him the No. 47 prospect. Sánchez entered 2018 as the Phillies number one prospect and one of the top prospects overall in the minors, pitching again for Clearwater. He has been compared to Pedro Martinez. On June 3 he was named Florida State League Pitcher of the Week, and he was named a Florida State League Mid-Season All Star. The Phillies shut him down after June 3 due to right elbow inflammation. He was 4–3 with a 2.51 ERA, and a 4.09 strikeout-to-walk ratio. Baseball America named him the Number 13 prospect in baseball, MLB Pipeline named him the No. 21 prospect, and Baseball Prospectus ranked him as the Number 23 prospect.
Miami Marlins
On February 7, 2019, Sánchez was traded with Jorge Alfaro, Will Stewart, and $250,000 in international bonus slot money to the Miami Marlins in exchange for J. T. Realmuto. He began the 2019 season with the Jacksonville Jumbo Shrimp. Sánchez was named to the 2019 All-Star Futures Game. In 2019 between Jacksonville and the Class A+ Jupiter Hammerheads he was 8-6 with a 2.76 ERA in 20 starts. Sánchez was added to the Marlins 40–man roster following the 2019 season.
