I could definitely see Brown playing the Stanley Johnson role this year (I just hope he doesn’t piss off LeBron via the media like Johnson did). I love Jaylen as a long-term piece for the Celtics; he’s big, athletic, and plays guards positions. His jumper has come a long way this season, and getting playoff experience as a rookie is a real advantage.
Brown struggled guarding LeBron in the regular season (duh, who didn’t?), but a lot of it was due to rookie mistakes like jumping the wrong way on picks and turning his head, allowing LeBron to go by him. He’ll make those mistakes again, but the big thing for him will be avoiding dumb fouls. He struggled with that this season, and giving ticky-tack fouls on LeBron is a good way to get blown out.