Brown (ankle/knee) was not spotted at Friday's practice, Evan Lazar of the Patriots' official site reports.
Brown was limited Wednesday and missed practice Thursday, with reports confirming a flare-up in his knee. He's managed chronic/degenerative knee problems throughout his career, typically managing to play even when the issue flares up. That said, the back-to-back absences from practice suggest Brown is in danger of missing Sunday's game at Miami, potentially leaving DeMario Douglas, Efton Chism and Kyle Williams as New England's top three WRs.