Pagan was sent to Triple-A Nashville on Wednesday.
Pagan has struggled over 12 appearances with Oakland this season, logging a 5.93 ERA and 1.76 WHIP with a 7:4 BB in 13.2 innings of relief. The 26-year-old will look to fix some issues at the Triple-A level before rejoining the Athletics at a later date. In a corresponding move, the club recalled Brett Anderson up from the minors ahead of his start against Seattle on Wednesday.