Dickerson, who turns 34 on May 22, was placed on the injured list during the first week of the season after a left calf strain. He was hitless in three at-bats through two games to start his first season with the Nationals.
A former All-Star (2017) and Gold Glove winner (2018), Dickerson is a career .281 hitter with 134s homers and 452 RBIs in 1,035 games with eight teams since his 2013 debut. He went 2-for-10 with a walk during a three-game rehab assignment at Rochester.
Alu, 26, was 1-for-9 with a walk in three games for the Nationals after making his major league debut last Tuesday. Abbott, 27, pitched two scoreless innings Sunday and has a 2.25 ERA in two relief outings for Washington this season. He is 0-5 with a 5.45 ERA in 25 appearances (10 starts) for the Chicago Cubs and Nationals over the past three seasons.