Weeks led off the 15th with a three-bagger off Aaron Loup (0-2) and scored when Crisp followed by lofting a fly ball to center field. The throw from Toronto's Anthony Gose was late, and the A's posted their major league-best 13th walk-off win of the season.
Travis Blackley (4-3), Oakland's seventh pitcher, earned the victory with three scoreless frames for the American League wild card-leading A's, who have won the first two contests of a four-game series.
Toronto's Jeff Mathis forced extra innings with a game-tying, three-run homer with two out in the ninth, but it wasn't enough for the Blue Jays, who dropped a season-high fourth straight.
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