Grading the 2023 KC Royals: James McArthur's rebound

The KC Royals trade for James McArthur did not yield immediate rewards, but his second-half performance wowed fans.
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KC Royals fans voiced their displeasure with the team trading for pitcher James McArthur earlier this season. The Royals trading with the Philadelphia Phillies for a player already designated for assignment was received as yet another move only a losing franchise would make. Many amateurs made the deal out to be franchise-altering, as Kansas City sent Dominican Summer League standout Junior Marin back to Philadelphia.

This trade could not have aged better for the Royals.

The KC Royals gambled on themselves by trading for James McArthur.

McArthur was a starter in the Phillies organization but performed well in spring training out of the bullpen. He continued to start games in Triple-A as he awaited his MLB debut. The 26-year-old McArthur had all the physical tools teams want on the mound. standing at 6 feet 7 inches. The Royals sported MLB's fourth-worst bullpen ERA when they made this trade, so the team could hardly be picky in looking for reinforcements.

McArthur reported to Triple-A Omaha but made his MLB debut on June 28 against the Cleveland Guardians. That lone inning could not have gone worse, as he gave up seven earned runs while facing 10 batters. The final score of 14-1 showed that the Royals were already losing badly, but McArthur's performance left a bad first impression. Thankfully, baseball is more about what a player has done lately than their first look.

McArthur returned to the big leagues in August, making five appearances from Aug. 6 through Aug. 16. He was better than his debut, but he walked more batters than he struck out while recording a 5.09 Fielding Independent Pitching (FIP). Better, but still hardly good, or an arm Royals fans felt comfortable seeing on the mound in high-leverage situations.

Royals fans would not see McArthur again until Sept. 2, the turning point for his prospects in Kansas City. He was an elite reliever as the season ended, making 12 appearances from Sept. 2 through Oct. 1. In 16 1/3 innings pitched, he had 19 strikeouts and no walks or runs allowed. He was the only American League pitcher in September and October to allow no runs and no walks in at least 10 innings pitched this season. He picked up his first career win and save, totaling four saves in his last six appearances.

Many Royals fans will understand that the Royals had nothing but pride to play for in September, but Kansas City trusting him in late-inning situations shows massive progression from his earlier debut.

McArthur's grade weighs his progression more than his debut game.

Let's look at the McArthur trade from a 10,000-foot level. The Royals traded a prospect years away from a possible MLB debut for a reliever worth .5 fWAR in his debut season. Here is how McArthur ranks among Kansas City relievers with at least 10 innings pitched following the trade deadline:

  • 0.93 ERA - 2nd
  • 1.50 FIP - 1st
  • 9.31 K/9 - 4th
  • 0.47 BB/9 - 1st
  • 20.00 K/BB - 1st
  • 0.62 WHIP - 1st

There are many signs saying McArthur was not only a competent MLB reliever but also the Royals' bullpen leader as the season progressed. This trade was a steal by Kansas City and a success story for the team's new-look pitching development. These are the moves that successful teams make and capitalize on. McArthur's season gets an A, with his debut being the biggest blemish.