Castillo signed a one-year, $4.2 million contract with the Reds on Friday to avoid arbitration, Robert Murray of FanSided.com reports.
The right-hander is in his first year of arbitration eligibility, so the $4.2 million is a significant figure despite him still being underpaid. Castillo had a 3.21 ERA, 1.23 WHIP and 89:24 K:BB over 70 innings last season, and he should sit at the top of Cincinnati's rotation in 2021 alongside Sonny Gray.