Barnes was traded to the Twins and assigned to Triple-A Rochester on Thursday, Brandon Warne of ZoneCoverage.com reports.
The 33-year-old played well for Triple-A Columbus, amassing a slash line of .274/.337/.535 with 24 home runs and 77 RBI so far this season. Given his veteran presence, Barnes could see some time with the major-league squad if more depth is needed as long as he continues to impress at the Triple-A level.