Manchester born right winger Jack Reynolds began his senior football career signing with Manchester City in July 1902, spending a season on the books at Hyde Road without making their first eleven. He joined Second Division Burton United in July 1903, making his Football League debut at Bolton Wanderers that September and scoring 6 times in 40 appearances during his only season for Burton. He joined Grimsby Town in April 1904 scoring 4 goals in 31 appearances before being signed by First Division Sheffield Wednesday for £275 in June 1905, spending two seasons at Hillsborough as mainly a reserve team player, making a single first team appearance in each of his two seasons with The Owls.
In May 1907 he joined Southern League Watford, where he scored 4 goals in 28 appearances, joining New Brompton (now Gillingham) in May 1908, where he scored 16 goals in 108 appearances over the next 3 seasons. He joined Rochdale in the close season of 1911, and finished his playing career with them a year later before starting a managerial career for which he is far better known.
Reynolds started his career as a coach with Swiss club St. Gallen in 1912, and after a two-year stay he left to become coach of the German national football team. The outbreak of World War One prevented that, and he moved to the Netherlands instead. In 1915, Reynolds started his 27-year association with Ajax, during which he set the bases of the Total Football system of playing later developed by Rinus Michels. During his three spells with the club (1915-1925, 1928-1940, and 1945-1947) they won the Eredivisie 8 times and the KNVB Cup once; Ajax had not won either prize before. He also managed Dutch club Blauw Wit from 1925 to 1928.
When the Nazis invaded The Netherlands in 1940 during World War Two, Reynolds was interned in Tost (now Toszek) in Upper Silesia (now in Poland), along with other foreign nationals including P. G. Wodehouse. After Reynolds retired in 1947, he lived in Amsterdam until his death in 1962. Three years later in 1965 a stand at the De Meer Stadion was named after him.
In 1919, Reynolds became the first manager to coach the Netherlands since the suspension of international football due to World War One. He assumed the honours for the match against Sweden on 9th June 1919. The Dutch won the match 3-1.
His brother Billy Reynolds played for Burton United and Grimsby Town, as well as Clapton Orient, Swindon Town, Croydon Common and St Gallen.