After making the team out of Spring Training, the rookie right-hander soon pitched his way into the closer's role and was the team's lone All-Star.
But Cook has hit a rough patch recently. In the series against the Blue Jays, he's blown two saves and given up tying home runs in the ninth inning on Friday and Saturday. Overall, he's blown four of his last six save opportunities, and his seven for the season are the most in the American League.
Before Sunday's game against the Blue Jays, A's manager Bob Melvin revealed that Cook's hold on the closer role may not be completely secure in light of his struggles.
"We'll continue to monitor that," Melvin said. "Obviously he won't pitch today [after pitching in three straight games]. We'll take all the variables into consideration like we do with anything. You have to support younger guys going through difficult times, [but] there are times that hypothetically you feel like you need to give somebody a break from a role.
"We've shown we can do that too. We'll figure that out here in the coming days."
Cook's biggest problems have come when pitching multiple days in a row. He has a 0.24 ERA in 38 innings when throwing on one or more days' rest, but he's allowed 12 runs in 9 1/3 innings in 11 games with no rest.