The Athletics optioned Ferguson to Triple-A Las Vegas on Monday.
With nine holds and one save over his 36 appearances. Ferguson had been serving as one of the Athletics' higher-level relievers this season, but he'll end up losing his spot on the 26-man active roster after a rough June in which he turned in a 15.58 ERA, 2.54 WHIP and 10:8 K:BB across 8.2 innings. The 31-year-old righty will give up his spot to righty Justin Sterner, who was recalled from Las Vegas.