The Athletics are expected to promote Arnold from Double-A Midland to Triple-A Las Vegas on Tuesday, Martin Gallegos of MLB.com reports.
One of the Athletics' top pitching prospects, Arnold will get his first taste of the Pacific Coast League on the heels of a magnificent stretch at Midland. Since serving up a season-high seven runs on 12 hits and three walks in a May 27 start versus Amarillo, Arnold has delivered a 2.43 ERA, 1.18 WHIP and 73:25 K:BB across 66.2 innings in his ensuing 13 starts.