Saints boss Mauricio Pochettino has confirmed the Kenyan remains on his shopping list.
"I've seen a lot of him and he's perfect," Watson told the Daily Echo.
"Obviously, I heard that he couldn't agree terms, but he is the perfect player that we actually need at Southampton.
"He's big, strong, wins the ball, gives it, turns defence into attack and he gets on the end of things from set pieces.
"Having someone like him in the middle of the park would probably free up Morgan (Schneiderlin) to do a bit more damage in the final third."