 After 267 appearances for Derby, Liverpool manager George Patterson secured his services for a £7,500 fee in December 1934.He immediately made his debut on 8 December in an away fixture at Stamford Bridge; Chelsea spoilt the day for Cooper by humbling the "Reds" 4–1.Cooper failed to hit the target for his new club (after only scoring once for Derby) although he was an excellent defender who was one of the toughest tacklers in the game.