Richard Sherman tells TMZ Sports if Antonio Brown is REALLY wanting to join the Niners ... he doesn't think it'd be a mistake, saying his time in S.F. has been great so far.
A.B.'s on his way out of Pittsburgh after causing tons of drama this past season ... and Jerry Rice says the All-Pro wideout wants to play next for the 49ers, "really bad."
So, when we saw Sherm hitting up Catch in L.A. on Thursday night, we had to ask if he'd welcome the WR with open arms.
"Good luck to him," the defensive back told us -- and when asked if he had advice to Brown added, "Go wherever makes you happy."
Of course, Sherman signed with the 49ers last March after a legendary career with the Seattle Seahawks -- and, despite the 4-12 record, Sherman says he's enjoying his experience in San Fran.
Besides being a superstar on the field, Sherman is also advocating for lifetime health insurance coverage for NFL players ... so, we asked how that fight is going too.
By the way, Sherman was super cool with us (as always) before leaving in a waiting SUV.