Guerra (elbow) signed a minor-league contract with the Athletics on Monday.
Guerra was a fairly prominent contributor out of the Oakland bullpen in 2021, maintaining a 4.11 ERA and 1.11 WHIP across 65.2 innings. However, Guerra underwent Tommy John surgery in April and missed the entire 2022 season. He was non-tendered by the club earlier in the offseason and will now have to earn back his spot on the 40-man roster once healthy.