Diamondbacks reliever Joe Mantiply to open season on 15-day IL

The Diamondbacks will be without top reliever Joe Mantiply start the season. Manager Torey Lovullo told reporters the southpaw will open the year on the 15-day injured list as he battles shoulder fatigue (via Nick Piecoro of the Arizona Republic). Arizona will carry Kyle Nelson on the active roster in his place.

Mantiply had a breakout 2022 campaign. The southpaw threw a career-high 60 innings over 69 appearances, posting a 2.85 ERA. Mantiply racked up grounders at an excellent 53.5% clip while punching out more than a quarter of batters faced. 

Perhaps most impressively, he kept his walks to a microscopic 2.5% rate, the second-lowest mark among relievers around the league.

That secured Mantiply his first All-Star nod and pushed him into high-leverage innings. 

The Snakes set out to deepen their bullpen this offseason with additions of Miguel Castro, Scott McGough and Cole Sulser. They’ve already lost Mark Melancon and Corbin Martin for extended stretches this spring, and now they’ll be down arguably their top reliever headed into the year. The team hasn’t provided much clarity on Mantiply’s return date.

To backfill the bullpen, the D-backs are turning to a few less proven arms. Right-hander Drey Jameson is moving to relief, the club announced over the weekend (relayed by Steve Gilbert of MLB.com). Ryne Nelson secured the fifth starter role and Arizona elected to carry Jameson out of the big league bullpen rather than send him back to Triple-A Reno. 

Jameson impressed over his first four MLB starts last season but has long faced questions from evaluators about whether he can hold up as a starter, due both to a rather slight frame and some inconsistency in his control.

Meanwhile, 23-year-old righty Carlos Vargas will get a season-opening bullpen job (as first reported by Eno Sarris of the Athletic). He’s already on the 40-man roster but hadn’t previously gotten a big league call. Arizona acquired Vargas from the Guardians back in November.

The Dominican Republic native split the 2022 season between Cleveland’s top two affiliates, combining for a 3.67 ERA with a decent 24.7% strikeout rate but an alarming 11.3% walk percentage across 34 1/3 innings. 

He managed a 13:4 strikeout-to-walk ratio in 10 1/3 frames of three-run ball while averaging north of 100 mph with his fastball this spring. He’s a volatile but possible high-upside arm for Lovullo to call upon in the middle innings.