Maybe 4th best player, (or 5th Smart), but an important piece. Hope he's back soon.
I'd argue he's our second best player after Kemba. A more efficient scorer than Tatum and our second best defender after Smart, with a slight edge over Hayward because of his aggressiveness / explosiveness.
I dunno how much more efficient he is than Tatum. Tatum shoots much better from the FT line and is a better shooter from deep, but Brown has the edge in 2P%. Tatum has a 1% advantage in TS%, turns it over a tiny bit less, but also generates less free throws (barely) than Brown.
I'd say Tatum has the edge in efficiency.
On any given night I think our second best player is one of our three wings.