After signing with the Yankees, Smith-Njigba made his professional debut with the Rookie-levelGulf Coast League Yankees, where he hit .289/.430/.422 with five home runs and 28 RBIs over 57 games. In 2018, he played with the Staten Island Yankees of the Low–ANew York–Penn League where he hit .191 with three home runs and 16 RBIs over 45 games, missing time due to injury. In 2019, he played for the Charleston RiverDogs of the Single–ASouth Atlantic League, with whom he earned All-Star honors.[4] Over 124 games, he batted .307/.405/.465 with 11 home runs, 74 RBIs, and 16 stolen bases.[5] He did not play in 2020 due to the cancellation of the minor league season because of the COVID-19 pandemic.[6]
Pittsburgh Pirates
On January 24, 2021, the Yankees traded Smith-Njigba (alongside Miguel Yajure, Roansy Contreras and Maikol Escotto) to the Pittsburgh Pirates in exchange for Jameson Taillon.[7] He was assigned to the Altoona Curve of the Double-A Northeast for a majority of the 2021 season.[8] He was placed on the injured list briefly at the end of July, but activated in early August.[9] He was placed back on the injured list in mid-August with a thigh injury, but was activated one month later.[10] Over 66 games, he hit .274/.398/.406 with six home runs, 40 RBI, and 13 stolen bases.[11] Following the end of Altoona's season in mid-September, he was promoted to the Indianapolis Indians of the Triple-A East with whom he appeared in seven games.[12] He was selected to play in the Arizona Fall League for the Peoria Javelinas after the season.[13] On November 19, 2021, the Pirates selected his contract and added him to their 40-man roster, protecting him from the Rule 5 draft.[14] He returned to the Indians to begin the 2022 season.[15]
On June 13, 2022, the Pirates promoted Smith-Njigba to the major leagues.[16] He registered his first major league hit the next night while pinch-hitting and recorded a double off of St. Louis Cardinals relief pitcher Giovanny Gallegos.[17] He played in three games, going 1–for–5. On June 17, he was placed on the 60-day injured list with a wrist fracture.[18]
In 2023, Smith-Njigba played in 15 games for Pittsburgh, going 4–for–32 (.125) with no home runs, five RBI, and one stolen base.[19] He was designated for assignment by the Pirates on January 31, 2024.[20]
On February 7, 2024, Smith-Njigba was claimed off waivers by the Seattle Mariners.[21] Ten days later, on February 17, he was designated for assignment.[22] On February 19, he returned to the Pirates on another waiver claim.[23] Smith-Njigba was optioned to Triple–A Indianapolis to begin the 2024 season.[24] However, he was designated for assignment following multiple roster moves on March 28.[25] Smith-Njigba cleared waivers and was sent outright to Triple–A Indianapolis on March 31.[26] He made 54 appearances for Indianapolis, hitting .212/.344/.330 with two home runs, 18 RBI, and six stolen bases. Smith-Njigba was released by the Pirates organization on July 6.[27]
Chicago White Sox
On August 7, 2024, Smith-Njigba signed a minor league contract with the Chicago White Sox organization.[28] He became a free agent after the 2024 season.[29]