A 20-year-old infielder for a Milwaukee Brewers farm team is in critical but stable condition after suffering a “cardiac event” when he was struck in the chest by a pitch.

Julio Mendez was hit by a pitch thrown by the Arizona League Angels’ Austin Krzeminski as Mendez batted in the ninth inning with one out and the Arizona League Brewers trailing 4-2 on Saturday night at Diablo Stadium in Tempe, Ariz. He fell to the ground and trainers rushed to the plate, followed shortly by paramedics (via Baseball America). He was then taken to a hospital.

In a statement Sunday, the Brewers confirmed the cardiac event and Mendez’s “critical but stable condition.”

Brewers General Manager David Stearns added that updates would be provided as they become available. “All of our thoughts and prayers are with Julio and his family,” he said.

A social media description from a fan at the game describes a scary scene, with trainers performing CPR and using a defibrillator.

Although details about the incidents and Mendez’s overall health are not yet available, studies have shown that the timing of the hit in a healthy person is critical. At issue is the timing of the strike and whether it occurred during a critical split-second in the heart’s pumping cycle. If the heart is relaxed, a blow can trigger a fatally irregular heartbeat.

It is not certain whether that’s what happened to Mendez, who was born in Venezuela and will turn 21 in October. The 5-foot-10, 140-pounder is hitting .255 in 35 games with the Brewers, an organization he’s been with since 2014. Krzeminski, the pitcher who hit Mendez, and others immediately asked for prayers for the player on social media.