Nuño, 27, was 3-2 with a 3.23 ERA (14 ER in 39.0 IP), 5 walks and 37 strikeouts in 6 starts with the Aces this season. He ranks second in the Pacific Coast League in strikeouts and fourth in innings pitched at the time of his promotion. Nuño made 31 appearances (28 starts) with the New York Yankees and D-backs in 2014 and posted a 4.56 ERA (82 ER in 161.2 IP). He was acquired by Arizona on July 6 for right-handed pitcher Brandon McCarthy and cash considerations. Marshall, 25, was 0-2 with a 6.08 ERA (9 ER in 13.1 IP) in 13 games with the D-backs this season. He tossed 1.1 scoreless innings in his last outing yesterday vs. the San Diego Padres.
This is a somewhat unexpected move, and it's not clear whether this means Nuño will be starting Friday's game against the Phillies, or if this is intended to provide some long relief for a bit, especially in the wake of yesterday's "all bullpen" outing. Nuño has been a starter in Reno, but the timing of the pick-up would suggest its intended as a holdover to prop up a relief crew likely to be wheezing a bit, with Daniel Hudson and J.C. Ramirez likely unavailable for at least tonight and tomorrow, having thrown 56 and 39 pitches respectively.
On that basis, it's perhaps surprising it wasn't Ramirez who was sent back down, to open up a slot for a fresh arm, But there seems to have been something not quite right with Marshall for a few weeks now, so hopefully this will give him the chance to get straightened out, and come back up, right as rain. In the meantime, we'll see if we can perhaps get Nuño the win in relief, which eluded him in 14 attempts as a starter last season!