Santos begins his first season with the Ducks and 11th in professional baseball. The right-hander spent nine seasons in the St. Louis Cardinals organization (2012-19, 2021) and one in the Washington Nationals system. He compiled a record of 24-31 with a 3.86 ERA, 12 saves and 458 strikeouts in 492.1 innings over 214 games (46 starts). The Dominican Republic native reached the Triple-A level with the Cardinals and the Double-A level with the Nationals.

The 29-year-old made a career-high 40 appearances across three different levels in 2021, compiling a 7-5 record with a 3.38 ERA, three saves and a career-best 2018 strikeouts in 72.0 innings. The righty also accrued a 3.00 ERA and two saves in 34 games (two starts) with High-A Palm Beach in 2019 and turned in a 7-4 record with a 2.99 ERA and three saves across 38 games (six starts) at Low-A and High-A in 2017. Santos was originally signed by the Cardinals as a free agent in 2012.