Day was born in Ebbw Vale and attended Pontygof School. After playing youth football with his home-town club, he moved to London where he began his career at non League clubCheshunt. In May 1931, he signed for Tottenham Hotspur as a trainee, being "farmed out" to the Spurs' nursery team Northfleet United, where he joined his former Ebbw Vale colleague, Eugene "Taffy" O'Callaghan. On 4 November 1933, Day made his only international appearance for Wales. The Football Association of Wales secretary, Ted Robbins, rang the secretary at Spurs, Arthur Turner, to enquire if he knew anyone who could help out the depleted Welsh team. Turner mentioned that he had a promising reserve half-back who he believed was Welsh, leading to Day being capped before having appeared in League football. The match at Windsor Park, Belfast against Northern Ireland ended in a 1–1 draw. Shortly afterwards, Day made his debut for the Spurs' first-team, going on to make 14 appearances in all competitions. The form of fellow-Welshman Tom Evans at right half prevented Day from becoming a regular in the Spurs' side, with nine of his League appearances coming in the 1934–35 season at the end of which Spurs were relegated from Division One. Despite his limited first-team appearances, Day made 139 appearances in the reserves in London Combination matches. He joined Millwall in 1936 where he spent one season and participated in five matches in the Third Division South, before joining Second Division Southampton on a free transferin the summer of 1937. At The Dell, Day took over from Cyril King for the first half of the 1937–38 season before King returned in December. Day was described as "a calm, neat player who specialised in the ground pass rather than the cleared high ball", he had solid defensive qualities, but tended to "dwell on the ball" and "his thoughtful distribution was sometimes marred by his being caught in possession". Day was never fully appreciated by the Dell crowd and moved on to Tranmere Rovers after 12 months. After a season with Tranmere in which Day made 32 League and one FA Cup appearance, at the end of which they were relegated from the Second Division, Day moved again to join Swindon Town in June 1939. He made his debut for Swindon at home to Aldershot on 2 September, the day before World War II was declared. Day remained with Swindon until June 1940, making a further 29 appearances in wartime competitions.