The 49ers are completing a trade with the Colts for Keenan Allen in a move that will strengthen San Francisco's injury-plagued wide receiver corps, sources told NFL Network's Ian Rapoport and ESPN's Adam Schefter.
The rebuilding Colts will receive a sixth-round draft selection, according to sources.
Allen, 34, joins a Niners team that is without starting wide receivers Mike Evans and Deebo Samuel, who both missed Sunday's victory over the Raiders. San Francisco also is without veteran Christian Kirk and rookie De'Zhaun Stribling, who are both on injured reserve, and Ricky Pearsall, who will miss the remainder of the season.
Despite the litany of injuries at receiver, the Niners enter Week 10 with the best record in the NFC at 7-1.
Allen is the third high-profile player dealt before Tuesday's deadline by the Colts, who traded away Quenton Nelson and DeForest Buckner last month.