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The Padres load up on depth, trading for Trevor Rosenthal, Mitch Moreland, and Jason Castro

A.J. Preller and the Padres front office had a busy weekend.

Kansas City Royals v Cincinnati Reds Photo by Joe Robbins/Getty Images

In three separate trades over this past weekend, the Padres acquired three new players to help further their playoff push. On Saturday, San Diego acquired reliever Trevor Rosenthal from the Royals and first baseman Mitch Moreland from the Red Sox. And, on Sunday, they added catcher Jason Castro in a deal with the Angels.

All of this should just be icing on the cake for the team, which has jumped out to a 21-15 start, good for the third-best record in the National League.

Behind Fernando Tatís Jr., who currently leads baseball in WAR; Manny Machado, who isn’t that far behind him; and a supporting cast that includes Trent Grisham, Wil Myers and a revamped Eric Hosmer, the Padres have assembled the best offense in the National League. The starting pitching has been solid, but the bullpen — hurting especially from the loss of Kirby Yates to the Injured List — remained a weakness.

That is why the Padres went out and acquired Rosenthal, who has bounced back in a big way this year. After carrying an infinite ERA through his first four appearances last year — and finishing the season at 13.50 and -0.3 WAR — Rosenthal signed a minor-league contract with the Royals. They were betting on a rebound, in hopes that Rosenthal would return to old form, like when he was the 11th-most valuable reliever from 2013 to 2017. Encouraging was the fact that Rosenthal’s velocity remained sharp, even as he struggled to get hitters out; his fastball averaged 98.0 mph last year, and still sits at 97.8 mph this year.

The control, however, didn’t return until 2020, making the Royals’ bet a successful one. Rosenthal has never been completely walk-adverse — he walked over 10 percent of hitters, even during his prime — but seeing his year-over-year walk rate drop from 30.6 percent to just 12.5 percent has been a major key for his success. He’s done a much better job cleaning up the pitches way out of the zone:

Rosenthal Pitch% by Attack Zone

Zone 2020 2019 2020 lg avg
Zone 2020 2019 2020 lg avg
Heart 33.0% 24.4% 25.6%
Shadow 40.3% 39.3% 42.3%
Chase 18.9% 20.7% 22.9%
Waste 7.7% 15.6% 9.2%

Rosenthal improved his control and started attacking hitters head-on, throwing more pitches in the heart of the zone than the average pitcher. It’s worked, however, as hitters have been held to just a .312 wOBA and a .294 xwOBA on batted balls in the heart of the zone. His stuff is good enough to challenge hitters, and in doing so, he’s cut out the walks, brought back the strikeouts and has pitched like one of the game’s better relievers. To date, Rosenthal has a 3.29 ERA, a 37.5 percent strikeout rate and just a 12.5 percent walk rate. That’ll play in the back of San Diego’s bullpen.

Offensive reinforcements came later on Saturday with the acquisition of Mitch Moreland, who is the third-best hitter in baseball coming into Sunday (min. 10 plate appearances). Moreland has had 79 turns at the plate, and he’s slashed .328/.430/.746 with eight homers and a 203 wRC+. He projects to be the Padres’ designated hitter the rest of the way, filling perhaps the one offensive hole the team had. Tommy Pham has the most plate appearances there, but a fractured hamate could keep him sidelined for the rest of the season.

Moreland’s offensive outburst looks legitimate, and even when he does inevitably cool off, the 106 wRC+ he put up from 2018 to 2019 would certainly play just fine. Moreland has absolutely mashed fastballs this season, to the tune of a .520 wOBA and .534 xwOBA. He has increased his launch angle year-over-year, and for the first time in his career, he is hitting more fly balls than ground balls. Because most of his damage has come on the fastball, pitchers may opt to throw him more breaking stuff as the season goes on. His fastball percentage year-over-year has dropped slightly — from 56.2 percent to 51.2 percent — but there doesn’t appear to be any in-season trend to suggest that pitchers are backing down:

Pitches considered “fastballs” include four-seamers, two-seamers, cutters and sinkers.

The Padres do have the ability to retain Moreland in 2021, if they so choose. He is playing out the rest of his one-year, $3 million contract, one that came with a team option for next year. San Diego can exercise that for an additional $3 million, with a $500,000 buyout if they do not.

But Moreland wasn’t the only position player the Padres added over the weekend. Jason Castro will also be donning the brown and gold, as added depth at the catcher position. Francisco Mejia, who has been on the Injured List, is nearing a return, however. In the interim, Austin Hedges has hit surprisingly well, slashing .217/.400/.522 in 32 plate appearances since Mejia went down. The Padres know that this won’t continue long term, given Hedges’ career 62 wRC+.

Enter Castro. The 33-year-old is a slightly-below-average bat for his career, though he has always had a good glove. The Twins platooned him with Mitch Garver last year, with Castro getting significantly more plate appearances against right-handed pitchers (230 PA) than lefties (45). It is not a surprise that this was the strategy given his career numbers:

Jason Castro career splits

vs. RHP 2365 .242 .329 .421 11.0% 27.0% 106
vs. LHP 719 .195 .260 .291 7.4% 31.6% 53

On the season, Castro is hitting .192/.323/.385 with a 98 wRC+ in 62 plate appearances. It’s been a fairly typical season for him. The defense looks slightly worse than his career averages, but it’s quite possible that the small sample gremlins could be playing a role there. His framing has been worth -0.5 runs this season after being +3.2 runs last year, so it’s not too egregious to start, but still something worth watching.

All told, the Padres did have to trade some players away in order to bring on these new additions. Outfielder Edward Olivares and a player to be named later went to the Royals, third base prospect Hudson Potts and outfield prospect Jeisson Rosario went to the Red Sox, and righty reliever Gerardo Reyes went to the Angels. Of these, Potts (11th) and Rosario (20th) were the only players listed on FanGraphs’ list of Padres top prospects prior to the season.

And, with the trade deadline today, the Padres are not done. They made a seven-player deal with the Mariners to acquire Austin Nola and have reportedly been in discussions with the Indians for Mike Clevinger. They’re rolling the dice on the shortened season, and given that they haven’t made the playoffs since 2006, who could blame them for keeping the foot on the gas?

Devan Fink is a sophomore at Dartmouth College and a Contributor at Beyond The Box Score. Previous work of his can be found at FanGraphs and his own personal blog, Cover Those Bases. You can follow him on Twitter @DevanFink.