In 2017, Gressel signed a contract with Major League Soccer and was selected in the MLS SuperDraft in the first round with the eighth overall pick by expansion side Atlanta United.

[4] In his freshman season, the Friars reached the championship match of the 2013 Big East Men's Soccer Tournament, before losing 3–2 against Marquette.

[5] The Friars ultimately earned an at-large bid into the 2013 NCAA Division I Men's Soccer Championship, where they reached the second round before losing to the fifth-seeded, Maryland.

[3] During his sophomore and junior seasons, Gressel earned honors on the Big East Conference All-Tournament teams for both the 2014 and 2015 editions of the tournaments.

[9] Gressel was also rewarded with the Golden Boot award for scoring the most goals during the 2016 NCAA Division I Men's Soccer Championship, during a quarterfinal run which saw Providence beat CAA Champions Delaware,[10] upset top-seeded and Big Ten Champions Maryland,[11] and defeat Big East rivals Creighton.

Gressel won the 2017 MLS Rookie of the Year honors,[18] playing mostly as a central midfielder for manager Tata Martino.

[23] On July 21, 2023, Columbus Crew acquired Gressel from Vancouver Whitecaps FC in exchange for $550,000 of guaranteed General Allocation Money ($275,000 in 2023 and $275,000 in 2024).

[24] On January 9, 2024, Inter Miami announced that they had signed Gressel as a free agent on a three-year deal with an option for a further year.

[25][26] Gressel made his 2024 Inter Miami season debut in a match against Real Salt Lake on February 25, 2024, ending in a 2–0 win.

[31] He made his Gold Cup debut off the bench against St. Kitts and Nevis, before assisting Gianluca Busio as a substitute against Trinidad and Tobago in the final group stage match.

[32] Gressel then started his first ever competitive match in the Gold Cup quarterfinal versus Canada, playing 90 minutes at right-wing as the US ran out as eventual winners on penalties to reach the semi-finals.