Plummer returned to Peoria in 2018, batting .205 with eight home runs and thirty RBIs in 104 games.[11] In 2019, he played for the Palm Beach Cardinals of the Class A-AdvancedFlorida State League, slashing .176/.312/.294 with five home runs and 29 RBIs over 96 games.[12] Covid canceled 2020.
Plummer began the 2021 season with the Springfield Cardinals of the Double-A Central.[13] On July 8, he hit three home runs, including a two run walk-off, in a game against the Tulsa Drillers, becoming the second Springfield player ever (alongside Nolan Gorman) to hit three home runs in a single regular season game.[14][15] St. Louis named him their Player of the Month for July after hitting .326 with six home runs, five doubles, one triple and 21 RBIs while reaching base safely in all 24 games for the month.[16] On August 7, he set a Springfield record after reaching base in his 33rd straight game, passing Tommy Edman who reached 32 straight times in 2018.[17] On August 23, after slashing .283/.404/.489 with 13 home runs, 46 RBIs, and 17 doubles over ninety games, he was promoted to the Memphis Redbirds of the Triple-A East.[18] Following the season’s end, after not being added to the Cardinals’ 40-man roster, Plummer elected free agency.[19]
New York Mets
On November 24, 2021, Plummer signed a one-year major league deal with the New York Mets.[20] Plummer made his Major League debut with the Mets on April 15, 2022 at Citi Field against the Arizona Diamondbacks. He entered the game in the ninth inning as a defensive replacement for Starling Marte in right field.[21] Two days later, he lined out against Matt Peacock in his first Major League plate appearance.[22][23] On April 18, He was returned to the minor leagues when Brandon Nimmo returned from the injured list.[24] Recalled on May 28, Plummer's first Major League hit was a game-tying bottom of the ninth home run against the Philadelphia Phillies on May 29.[25] He became the 14th player in Mets history to hit a home run as their first career hit; the first since Jeremy Hefner during the 2012 season. After hitting a home run in his second straight game in a win against the Washington Nationals, Plummer became the first player in Mets history to hit a home run in each of his first two career starts. On August 16, 2022, Plummer was designated for assignment. He cleared waivers and was sent outright to the Triple-A Syracuse Mets on August 19.[26] He elected free agency following the season on November 10.[27]
Cincinnati Reds
On February 3, 2023, Plummer signed a minor league contract with the Cincinnati Reds organization.[28] Plummer was released by the Reds on March 27.[29]