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Usually, retirements end because a player has decided after weeks of agonizing that he wants back in. As to Bills receiver Percy Harvin, it wasn’t that complicated.

Per a source with knowledge of the situation, the receiver-needy Bills called Harvin on a whim, asking whether he wanted to return. He considered it briefly and decided, “Why not?”

He knows the coaches, the players, and the offense. And he’s healthy, something Harvin wasn’t for most of the final years of his career.

Still only 28, Harvin was the NFL’s offensive rookie of the year in 2009 with the Vikings. He was an early-season league MVP candidate in 2012 before an ankle injury and general dysfunction ended his time in Minnesota.

Harvin has a history of being unpredictable. Which means that he soon could be retiring again, once he begins to experience any of the things that made him retire in the first place.