The Columbus Crew fired head coach Caleb Porter on Monday after Sunday's loss eliminated them from post-season contention.
The Crew could have clinched a berth with a draw against Orlando City SC but instead lost 2-1.
Orlando City converted a penalty kick in the 84th minute to snap a tie and defeat the Crew.
Columbus also played to a tie with expansion Charlotte FC on Wednesday.
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Porter recorded a 45-43-37 regular season record and helped the club secure an MLS Cup (2020) and the Campeones Cup (2021).
"This is not a decision we took lightly, and I need to first and foremost thank Caleb for his tireless efforts for the Crew during his four seasons with the Club," Crew general manager Tim Bezbatchenko said in a news release.
"Caleb will forever be a part of Black & Gold history as the second star above our crest from 2020 is a testament to his contributions and what we were able to bring home during a special year."
Bezbatchenko confirmed that assistant coaches Pablo Moreira, Tim Hanley, Eric Quill also will not be retained.
Hanley's contract is up this year. Another assistant, Blair Gavin, left for another coaching position.