He made 14 relief appearances for the team, and was promoted to the Lansing Lugnuts of the Single–A Midwest League to end the season.

[3] He spent the entire 2011 season in Lansing, making 44 appearances and posting a 5–1 record, 2.32 ERA, 99 strikeouts, and 13 saves in a career-high 66 innings pitched.

[3] Barnes made just four appearances totaling three innings pitched in 2013 before being shut down due to a rotator cuff injury.

[3] In the offseason he made 4 relief appearances for the Gigantes de Carolina of the Puerto Rican Winter league.

[3] He began the 2016 season in New Hampshire, and after pitching to a 1.01 ERA in 352⁄3 innings, was promoted to the Buffalo Bisons of the Triple–A International League in June.

[5] He made his MLB debut that night, holding a 2–1 lead with a scoreless inning of relief against the Houston Astros that included strikeouts of Alex Bregman and Carlos Correa.

[9] On October 8, Barnes was added to the Blue Jays' American League Division Series roster after Francisco Liriano suffered a concussion.

[10] On May 23, 2017, Barnes earned his first major league win after pitching 12⁄3 scoreless innings against the Milwaukee Brewers in a game the Blue Jays won 4–3.

[15] On December 6, Barnes was voted the Blue Jays' Rookie of the Year for 2017 by the Toronto chapter of the Baseball Writers' Association of America.