In his first season for the Saints, he was playing in the War League and in friendlies, and made a total of 39 appearances, scoring 12 goals, of which 10 were penalties, thus making him the club's second highest scorer behind Bill Rawlings.
In 1919, after the end of hostilities, professional football restarted and for the next seven seasons he was a virtual ever-present at right back, forming a successful full-back partnership with Fred Titmuss.
At first these were resisted, but with money needed to finance the purchase of The Dell, Southampton reluctantly accepted an offer of £3,250 from Herbert Chapman's Arsenal in spring 1926, and he was on his way to Highbury.
Despite being an FA Cup and League-winning captain, he never won any further England caps to add to the one he picked up at Southampton, with Roy Goodall and Tom Cooper keeping him out of the national side.
Parker moved back to his old club Southampton in March 1937, taking over from George Goss who had acted as manager since the previous summer without any real success.
Over two seasons he spent £9,000 on new players, bringing in wingers Harry Osman and Billy Bevis, goalkeeper Sam Warhurst and centre-half Bill Dodgin.
In June 1943, after a row with the Saints' board, he resigned his position to take up employment outside football as a ship's surveyor in Southampton Docks with Lloyd's registry.