on july 4, 2017, stevens was reunited with his former college player gordon hayward when hayward signed a contract to play for the celtics. in the 2017–18 season, the celtics' roster saw a massive change, as two-time all-star isaiah thomas was traded to the cleveland cavaliers in exchange for kyrie irving. stevens and the celtics went 55–27, finishing the season as the second seed in the eastern conference, despite losing hayward for the season to a broken ankle in the first game of the season and irving missing significant playing time due to knee injuries. despite irving missing the playoffs, stevens led the celtics on a deep playoff run, losing to the cleveland cavaliers in seven games in the eastern conference finals. stevens was considered a front runner for the nba coach of the year award, but lost to dwane casey of the toronto raptors.