He has never submitted anyone, and 2 of his 3 losses were by submission.
I know ground isn't all submission, but I'm just saying. Plus, usually you have to get the take down to initially be effective on the ground, and Silva can't take anyone down. He is a striker. ALL of his wins are by way of strikes. His ground game isn't horrible, but anyone with standard BJJ and minor wrestling skills will clown him on the floor.