PHOENIX — A's manager Bob Melvin said before Saturday's game against the Arizona Diamondbacks that he is switching to a closer-by-committee approach after Brian Fuentes' second ninth-inning meltdown the night before.

Fuentes, Grant Balfour and Ryan Cook will all split closer duties depending on their availability and individual matchups, according to Melvin.

"I feel like we have three closers now," he said. "We'll do the best we can to match up."

Balfour won the closer's job in spring training but was demoted in mid-May after struggling. Fuentes took over and had success initially, but he has allowed walkoff three-run homers in two of his past four outings, and his three blown saves are tied for second-most in the American League.

Cook, a rookie right-hander who has been unscored upon in 23 of his 24 appearances, provides the most intriguing option because of his dominance in the setup role.

"He could end up pitching the ninth," Melvin said, "but if the bases are loaded with two outs in the eighth, he might be (the best option)."

Melvin prefers having one clear-cut option in the ninth but said of his current closer situation: "At this point in time we're having a bit of an issue."