Colorado Rockies third baseman Nolan Arenado had already racked up a single, double, and triple heading into Sunday's final frame, and the San Francisco Giants had just taken a 5-3 lead by scoring three runs in the top of the ninth inning.
After the Giants turned it over to Mark Melancon for the save, Raimel Tapia made it a one-run game by scoring on a DJ LeMahieu single. Tapia joined Charlie Blackmon on the bases, representing the winning run with one out and Arenado coming up.
In his fifth at-bat of the game, Arenado hit a home run to complete the cycle and walk off the Giants, who have now dropped six straight. Colorado has won five in a row.
It's the fourth cycle of the 2017 season as Arenado joins Wil Myers, Trea Turner, and Carlos Gomez for the single-game achievement.
The last player to hit a walk-off homer to complete the cycle? None other than Arenado's teammate, Carlos Gonzalez.