The upcoming years for AEK and Papaioannou were almost ideal, as he showed that he was the one to take the leader role from Nestoridis in the team, pushing them as high as he could to lead them to success. His appearances and achievements put him quickly in the heart of the crowd. The fans adored him and he rewarded them with passion for the yellow-black jersey. On 29 September 1963 he scored a brace in the away defeat with 5–4 against Panathinaikos. He scored his first hat-trick on 16 October 1963 scoring all three goals against Aris at home. It did not take him long enough to score another one, as he did 2 months later against Ethnikos Piraeus in a 4–0 win. Papaioannou scored a goal in the imposing 6–1 against Olympiacos on 6 January 1964. He also scored 4 of the total of 7 goals of his team against Anagennisi Arta for the Cup, on 26 April 1964. At the end of the season he won his first Cup with AEK, even though the final was scratched due to the suspension of the semi-finalists, Panathinaikos and Olympiacos from the competition. In 1964 he ended the season as the league's top scorer with 29 goals, ending the 5-year winning streak of Nestoridis.
