Three Takeaways From the Royals’ Trade of Emmanuel Rivera for Luke Weaver

The Royals haven’t made any major moves so far with less than 24 hours to go before the August 2nd Trade Deadline. However, this afternoon, the Royals made a “minor” move by trading away third baseman Emmanuel Rivera to the Arizona Diamondbacks for pitcher Luke Weaver.

At first glance, it seems like an odd move, especially with Rivera being a lefty masher this season (.892 OPS against lefties), and with Weaver carrying a 7.71 ERA with the Diamondbacks in 12 outings and 16.1 innings pitched this season. However, the move could be a win-win for both the Royals and Diamondbacks and set up the Royals not just for another move by tomorrow’s deadline, but this offseason as well when it comes to determining the 40-man roster.

Hence, here are three quick takeaways from the Royals’ acquisition of Weaver, and what Royals fans should expect going forward in the coming day as we reach the official Trade Deadline.

Don’t Judge Weaver Solely By His 7.71 ERA

It is easy to look at Weaver’s age (28 years old) and his ERA and think that this move doesn’t make any sense for the Royals. On the other hand, a deeper dive into Weaver’s metrics present a more interesting case.

Weaver’s inflated ERA is mostly fueled by one bad spot start against the Minnesota Twins on June 18th where he gave up nine runs on 10 hits in 3.2 IP. When looking at his “reliever only” splits this year, his profile looks a lot better.

What is also interesting about Weaver is that his FIP is only 2.69 and his xERA is only 4.91, which greatly contrasts his abnormally high ERA. Weaver, due to that rough outing against the Twins, has been also hurt by a rough batted ball and runners-on base luck. His BABIP is currently .434 and his strand rate (LOB%) currently is 55.9 percent. Those numbers are bound to improve in his new surroundings in Kansas City (Kauffman is much more pitcher-friendly than Arizona’s Chase Field), especially as he gets more innings out of the Royals bullpen.

In fact, Weaver’s numbers have been trending in the right direction over the last month, as he has posted a 1.13 ERA in eight appearances and eight innings pitched in the month of July.

Here’s how his month-by-month splits look, via Fangraphs.

Weaver is also trending in the right direction batted-ball luck-wise, as his BABIP was only .200 in July, and his groundball to flyball ratio increased from 1.50 in June to 1.60 in July.

The ERA is ugly, but Weaver is a much better reliever than that 7.71 number indicates. That is a good thing for this Royals bullpen, which ranks 29th in reliever ERA this season.

Weaver Brings A “Control” Profile to the Royals Bullpen

The Royals bullpen has struggled to limit walks, as they rank last in Major League Baseball in BB/9.

When it comes to upgrading this bullpen, the Royals need a reliever who can not only maximize the strikeouts but limit the walks, especially in high-pressure situations.

And thankfully, Weaver has that kind of profile, based on his last three seasons with the Diamondbacks.

Even though he was drafted and initially developed as a starter in the Cardinals organization, the Diamondbacks moved him to relief this season. So far this year, his reliever profile is very similar to his one as a starter: he keeps the walks low while striking out a decent number of hitters.

Here’s a look at Weaver’s career strikeout to walk (K/BB) numbers, both a per/9 and percentage end, according to Fangraphs.

Notice that Weaver’s K/BB ratio has been under three only once, and his K/BB percentage has been under 15 percent once as well (both numbers came in 2018). Those are stellar numbers, even if it didn’t necessarily result in an elite starter’s profile with the Cardinals and Diamondbacks.

Utilized primarily as a reliever this year, he has improved his K/BB ratio by 0.70 points and K/BB percentage by 2.4 points as well. That has been primarily driven by an increase in strikeouts (1.97 points on a K/9; 1.6 percentage points on a K rate end), and a dip in walks on a BB rate end (one percentage point specifically).

To compare to the Royals bullpen, Weaver’s 3.80 K/BB ratio would be the second-best mark of Royals relievers with 10 or more innings pitched this season, behind only Taylor Clarke, whom Weaver played with last year in Arizona.

Additionally, we have also seen Weaver increase his K rate as of late. After being mostly slightly below league average for most of the year, Weaver has seen his K rate spike up above league average over his last few outings, as evidenced by his Statcast rolling breakdown.

Weaver’s arsenal is primarily a four-seam and changeup combo, which he throws 60.3 percent of the time and 23.3 percent of the time, respectively. His best strikeout pitch this season has been his changeup, which has produced a whiff rate of 40.5 percent and a K rate of 36.8 percent, according to Statcast data.

Here’s a recent clip of Weaver utilizing his changeup effectively low and inside to San Francisco’s Wilmer Flores, who nearly comes out of his shoes in his swinging strikeout.

The Royals bullpen needs relievers who keep the ball in the strike zone, and who can generate a good number of whiffs to boot (their bullpen K/9 ranks 26th in the league).

Weaver, if effective, can check both of those boxes for the remainder of 2022 and for 2023 (he will be up for his final year of arbitration in 2023).

The Writing May Have Been on the Wall for Rivera Anyways

There’s no question that Rivera has been a serviceable platoon bat at the third-base position this year. That being said, it is unlikely he would’ve been a long-term solution at the position, especially after they optioned him recently to Omaha once Salvador Perez returned off the IL.

The hot corner has been a sore subject for the Royals ever since Bobby Witt, Jr. was moved back to his natural position of shortstop after the Adalberto Mondesi season-ending ACL injury. The Royals have thankfully avoided putting Hunter Dozier there (he was pretty poor defensively last year), and while Nicky Lopez can handle the position defensively, his bat doesn’t profile well at third. While Rivera has had some decent streaks with the bat, his struggles against right-handers (63 wRC+ against righties) and his issues in the field (ranked in the 12th percentile in outs above average), made him a platoon player at best.

Alex Duvall of Royals Farm Report said it best on Twitter in that Rivera was a fun player who was worth rooting for (he always reminded me of a better Cheslor Cuthbert who I had a soft spot for), but was probably not going to figure into the Royals’ long-term plans (which explains why he was demoted to Omaha recently).

Going into this offseason, the Royals will have some tough roster decisions to make, especially when it comes to deciding who to protect from the Rule 5 Draft. Additionally, the Royals also have a plethora of guys coming up who can play third base, though none have necessarily proven it at the Major League level. Those players include Nate Eaton and Michael Massey, who haven’t played much third this year but have proven they can handle the position in their Minor League careers (Eaton was primarily a third baseman before moving primarily to the outfield in Omaha in 2022).

At the end of the day, while Rivera would have been a nice platoon bat, I’m not sure he fits on a rebuilding team that is trying to figure out who will be part of this roster in the next two to three years. If anything, I could’ve seen him as a DFA casualty to clear a roster spot for someone this offseason.

Thus, the Royals essentially got a reliever for a player they probably were going to part away with soon.

The Royals get some bullpen help and Rivera gets a fresh start in another rebuilding organization.

To me, that’s a win-win for Kansas City and Arizona.

Photo Credit: Matt Kartozian-USA TODAY Sports

8 thoughts on “Three Takeaways From the Royals’ Trade of Emmanuel Rivera for Luke Weaver

  1. […] Not only does Witt have to compete with Nicky Lopez, who should’ve been a Gold Glove finalist at shortstop last year, but he will likely battle with Maikel Garcia and maybe Adalberto Mondesi again this coming Spring (if Mondesi is healthy of course). That not only puts pressure on Witt but also gives manager Mike Matheny a reason to move him off the position, especially since there aren’t a lot of great options at third base for the Royals both at the Major and Minor League level after the Emmanuel Rivera trade. […]


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