Hundreds of supporters swarmed on to the pitch at the final whistle of their victory over MK Dons and former England and Leeds star Smith was surrounded.
Dons boss Karl Robinson ran on to frantically get Yorkshire-born Smith to the safety of the tunnel.
Robinson said: "Alan was punched, kicked, spat at - the lot. I ran on and had to push supporters off him.
"I thought I might be able to calm things down. But one or two mindless idiots have spoiled what was a wonderful game.
"English football has moved on immensely and scenes like that aren't great."