After the war Kelly disagreed with Joe Mercer. Kelly accused Mercer of not trying in an international against Scotland, but in reality Mercer had sustained a severe cartilage injury. Even after consulting an orthopaedic specialist, Kelly refused to believe him and Mercer had to pay for the surgery himself (after 14 years with the club). Understandably upset, Mercer moved in 1946 for £9,000 to Arsenal, although he commuted from Liverpool. Theo Kelly brought Mercer's boots to the transfer negotiations to prevent Mercer having a reason to go back to say goodbye to the other players at Everton.