After his sophomore year at Kennesaw State, he played collegiate summer baseball for the Bourne Braves of the Cape Cod Baseball League (CCBL), where he was named the league's most valuable player and Perfect Game's College Summer Player of the Year.

Blue Jays GM Alex Anthopoulos had intended to assign Pentecost to the Vancouver Canadians of the Class A-Short Season Northwest League.

[20] Prior to the start of the 2016 minor league season, Pentecost was ranked 9th on MLB's top 10 catching prospects list.

[22] On May 12, Pentecost appeared in his first game in over 16 months, and hit the first home run of his professional career in a 5–0 win for the Lugnuts.

[24] After hitting .314 with seven home runs and 34 RBI the Lugnuts in 62 games, Pentecost was promoted to the Advanced-A Dunedin Blue Jays.

He was limited to 72 games due to two separate disabled list stints, and hit .274 with nine home runs and 54 RBI.

[27] He spent the 2018 season with the New Hampshire Fisher Cats of the Class AA Eastern League, hitting .253 with 10 home runs and 52 RBI in 89 games.