He made his professional debut in 2012 with the Rookie-level Gulf Coast Marlins,[7] batting .223/.337/.338 with two home runs and 15 RBIs in 148 at bats over 47 games.[8] In 2013, he played for the Class A- Batavia Muckdogs and the Class A Greensboro Grasshoppers, batted a combined .262/.327/.416 with three home runs and 22 RBIs in 233 at-bats over 63 total games.
In 2014, he returned to Greensboro,[9] slashing .308/.371/.444 with nine home runs and 58 RBIs in 403 at-bats over 99 games. His 24.7% line drive percentage was third-best in the league.[1] During the season he injured his right hand during a slide, later suffered a nasal fracture when he was hit by a pitch, and later again hit the injured list, this time with a groin strain.[1]
He spent 2015 with the Class A+ Jupiter Hammerheads where he batted .268/.318/.366 with 67 runs (4th in the Florida State League), a career-high 32 doubles (2nd), five home runs, 52 RBIs, 10 sacrifice flies (leading the league), and a career-high 18 stolen bases (though he was caught stealing 10 times) in 515 at-bats over 136 games.[10] In the Arizona Fall League, playing for Mesa he batted .323/.364/.452 with one home run and seven RBIs in 62 at-bats.[2][1] He was an AFL Rising Star in 2015.[11]
He spent 2016 with the AA Jacksonville Jumbo Shrimp where he compiled a .238/.307/.375 slash line with 11 home runs and 67 RBIs in 480 at-bats over 130 games. He was a Southern mid-season All-Star and an MILB.com Organization All-Star in 2016.[11] He spent 2017 back with Jacksonville where he batted .282/.323/.427 with four home runs and 30 RBIs in 234 at-bats over 61 games.[12] He broke his right hand in an outfield collision and missed almost three months of the season.[1]
Dean made his Major League debut on August 15, 2018, against the Atlanta Braves, going 0-for-3.[13] In his first Major League season, Dean hit .221/.279/.363 with 16 runs scored, four home runs, and 14 RBIs in 113 at-bats over 34 games in left field.[14] In 2018 in the minors for Jacksonville and AAA New Orleans he batted .345/.410/.511 with 71 runs, 12 homes runs, and 68 RBIs in 397 at-bats over 109 games.[8] He was an MILB.com Organization All-Star in 2018.[11]
In 2019 with Miami he batted .225/.261/.404 with 6 home runs and 21 RBIs in 178 at-bats.[8] That season with New Orleans he batted .337/.401/.635 with 18 home runs and 57 RBIs in 252 at-bats over 73 games; he also was one-for-three for the GCL Marlins.[1]
St. Louis Cardinals
On January 14, 2020, Dean was traded to the St. Louis Cardinals for Diowill Burgos.[15] He appeared in only three games during the season, going one-for-four with three walks, while missing time due to injury.[16] During the season he was put on the injured list with a right elbow strain.[16]
In 2021 with the St. Louis Cardinals he batted .233/.342/.400 with one home run and 7 RBIs in
30 at-bats in 22 games.[1] In the minors, with Triple–A Memphis and Single–A Palm Beach he batted .246/.368/.456 with two home runs and 10 RBIs in 87 at-bats in 18 games.[1] During the season he suffered a fractured left wrist.[17][18]
Through 2021, in the major leagues, he had played 83 games in left field, 9 in right field, and 6 at first base.[1] In the minors he had played 491 games in left field, 142 in right field, 26 at first base, and 14 in center field.[1]
San Francisco Giants
On November 5, 2021, Dean was claimed off waivers by the San Francisco Giants.[19] He was designated for assignment on March 20, 2022, to create room for the newly signed Matthew Boyd, and sent to Triple-A on March 27.[20] With the Triple-A Sacramento River Cats in 2022, he batted .268/.345/.467 in 392 at-bats, with 68 runs, 5 triples (10th in the Pacific Coast League), 17 home runs, 55 RBIs, and 10 stolen bases in 12 attempts.[21][22] He played 59 games in right field, 27 in left field, 16 at DH, 8 in center field, and 6 at first base.[22]
On September 9, Dean had his contract selected to the active roster.[23] In 3 games for the Giants, he went 3-for-8 with a walk.[22] On November 9, Dean was removed from the 40-man roster and sent outright to Triple-A Sacramento.[24]
LG Twins
On December 22, 2022, Dean signed with the LG Twins of the KBO League.[25] Dean was named a KBO All-Star in 2023.[26] In 139 games for the Twins, he batted .314/.376/.517 with 23 home runs, 95 RBI, and 7 stolen bases.
On November 16, 2023, Dean re–signed with the Twins on a one–year, $1.3 million contract.[27]