Why would he grab my shoulders?

So this guy who I'm kind of friends with, he's one of my friend's brother's friends (that's a mouthful), and I've hung out with him a couple times. We also play on the same sports team so we see each other every now and then. Today we had a game and first he just tap my shoulder and kept walking.. you know that stupid way you try to "trick" people. Then, later after on of our games he was walking behind me and he grabbed my shoulders for a couple seconds and let go. Why would he do that? Just because... or could it be a sign he likes me?
Why would he grab my shoulders?
Post Opinion