The 27-year-old Allen has a .239 average with eight homers and 57 RBIs in 557 at-bats and 221 games over four seasons with Cleveland (2017-20) and San Diego (2020). Allen hit .154 with one homer and four RBIs in 26 at-bats over 16 games last year. He was designated for assignment on Dec. 31.
A San Diego native, Allen is not yet eligible for salary arbitration.
Reeves, 27, is 20-7 with a 2.30 ERA in 12 starts and 125 relief appearances over five minor league seasons. He did not get in a game last year, when the minor league seasons were canceled due to the coronavirus pandemic.