Sentence:  It dawns on you that instead of a lump to fill the seat across the bridge table from you , he was a man , and that because Gratt Shafer was making you miserable , you were passing it down to him , to Gratt Shafer 's <WSD>substitute</WSD> , that other guy . 
Meaning of the word marked with <WSD> tags:  a person or thing that takes or can take the place of another