The move was made Tuesday, a day after coach Doug Marrone announced Spiller was set to be activated from the reserve/injured designated to return list. Spiller missed eight weeks since breaking his collarbone.
Marrone wants to see how Spiller looks in practice before determining whether he can play Sunday, when Buffalo (8-6) plays at Oakland (2-12).
Summers became expendable after his playing time began to dwindle. The third-year player started seven of Buffalo's first nine games before being listed inactive in each of the past four.
Used mostly as a blocker, Summers had six carries for 17 yards and a touchdown, and five catches for 9 yards this season.
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