Barnes was optioned to Triple-A Buffalo prior to Friday's game, Mike Wilner of BlueJaysTalk reports.
Barnes has appeared in 32 games for Toronto this season, logging a 4.60 ERA and 1.60 WHIP with a 27:17 K:BB across 29.1 innings of relief. He will make room for Sam Gaviglio on the active roster, who is set to return from paternity leave at some point this weekend.