Arihara elected free agency Sunday.
The Rangers outrighted Arihara to Triple-A Round Rock on Wednesday.
Arihara was designated for assignment Sunday.
Arihara (1-3) took the loss against the Blue Jays on Saturday, allowing 11 runs on 12 hits and five walks while striking out one over three-plus innings.
Arihara is scheduled to start Saturday's game against the Blue Jays at Globe Life Field.
The Rangers announced Wednesday that Arihara has been moved to the bullpen, Levi Weaver of The Athletic reports.