The Patriots placed Keene (undisclosed) on the PUP list Thursday, Zack Cox of NESN.com reports.
Keene can be activated from the PUP list at any time during training camp, but given that he's coming off an unimpressive three-catch rookie season, it will be somewhat concerning if he has to miss a significant number of practices. With Hunter Henry and Jonnu Smith having joined New England's tight end corps in free agency, it will be pivotal for Keene to make the most of every opportunity he's given through training camp and the Patriots' preseason slate.