Yamamoto Yoshinobu, a 27-year-old Japanese pitcher for the Los Angeles Dodgers, allowed his first grand slam home run since making his Major League debut. His ERA also broke the 0.00 mark.

On the 9th (Korean time), Yamamoto made his start in an away game against the Arizona Diamondbacks at Chase Field in Phoenix, Arizona, pitching 5 innings, allowing 6 hits (2 home runs), 1 walk, 1 hit by pitch, striking out 4, and giving up 5 runs, resulting in a loss for the Dodgers, who fell 3-5.

Before this appearance, Yamamoto had a record of 4 wins and 2 losses with an ERA of 0.90 over 7 games (40 innings), striking out 49 batters. As the only pitcher in the Major League with a sub-1.00 ERA, expectations for the Cy Young Award were high, but he collapsed on this day, allowing 5 runs.

Yamamoto threw 44 pitches without allowing a run through the 3rd inning but fell apart in the 4th. After allowing a walk to Pavin Smith, he gave up an infield hit to Josh Naylor. Then, he faced Eugenio Suárez with a favorable count of two strikes, but the third slider he threw aimed inside resulted in a hit by pitch, creating a no-out, bases-loaded crisis.

At this point, he allowed a grand slam home run to Gabriel Moreno. After falling behind in the count with two balls in a row, he threw a cutter in the middle on the third pitch for a grand slam to right field. It was Moreno's first home run of the season and the first grand slam allowed by Yamamoto.

In the 5th inning, Yamamoto also allowed a solo home run to Ketel Marte, finishing with 5 innings and 5 runs allowed, leaving him with regrets. Previously, he had given up a total of 7 runs (4 earned runs) in 7 games, but he allowed more earned runs in just one day. He threw a total of 88 pitches, with a top speed of 95.9 mph (154.3 km/h), an average of 94.8 mph (152.6 km/h), including 32 four-seam fastballs, 23 splitters, 16 curves, 8 cutters, 6 sinkers, and 3 sliders.

Yamamoto's grand slam allowed on this day reminds one of Dodgers ace Ryu Hyun-jin (Hanwha Eagles) from 2019. That year, Ryu performed phenomenally in his first 23 games with an ERA of 1.64 over 148⅓ innings, but he collapsed during a game against the New York Yankees on Aug. 24, allowing 9 hits (3 home runs), 1 walk, striking out 7, and giving up 7 runs over 4⅓ innings, causing his ERA to surge to 2.00 and breaking his sub-1.00 record.

The grand slam home run hit by Didi Gregorius in the 5th inning was particularly painful. It marked Ryu Hyun-jin's first grand slam allowed in the Major League. Ryu finished the year with an ERA of 2.32, ranking first in the National League, but he regretted that his earlier sub-1.00 record was broken by mid-August. Had he maintained a sub-1.00 ERA, he might have had a chance at becoming the first Asian pitcher to win the Cy Young Award.

Yamamoto has not yet faced as severe a shock from a grand slam as Ryu Hyun-jin did, since the season is still early. However, the fact that he collapsed after a 5-day rest on his first appearance is a concerning factor. Yamamoto, who was used to pitching once a week during his time in Japanese professional baseball, did not have a single 4-day rest appearance in his rookie year in the Major League last year. He had the most 5-day rest appearances, with 11. This year, he maintained a 6-day rest rotation but made this appearance after 5 days of rest with unfavorable results.

According to SportsNet LA, the Dodgers' dedicated broadcast network, manager Dave Roberts commented on Yamamoto's struggles after the game, saying, "I don't think it was because he had one less day of rest. He doesn't seem to be affected by fatigue. His stuff was good, and the fastballs had power, but there were a few pitches that were slightly outside the zone," diagnosing it as a control issue.

Yamamoto also stated, "Overall, my stuff wasn't bad, but the grand slam decided the game," adding, "I gave the opposing team opportunities with the walk and hit by pitch. I tried to overcome it somehow, but it didn't work out well. The opposing hitters were excellent."

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