Ritchie was affectionately known as "Fat Cat" due to his burly build. He was selected for Australia's 1982-83 tour of Pakistan as a middle-order batsman replacement for Greg Chappell. He scored his first century, 106 not out, in his second Test at Faisalabad. He was unable to force his way into the Australia side over the 1982-83 and 1983-84 summers but was picked on the 1984 tours of the West Indies and India and made the Australian side over the 1984-85 summer. He was a fixture in the middle order between 1985 and 1987 that included the 1985 The Ashes tour to England, where he scored his highest score 146 at Nottingham, the 1986 tours of New Zealand and India, and the 1986-87 England tour of Australia.

He was famously referred to by Allan Border at the 1986 Madras Tied Test versus India. Batsman Dean Jones was contemplating going off "retired ill" after vomiting at the crease and Border suggested that "a tough Queenslander" (Ritchie) could hack the conditions instead. Jones stayed on and scored a double century.

1980/81

Ritchie made his first class debut in 1980-81, playing for Queensland against Victoria. He batted once, scoring 7. However he impressed in his third match, a tour game against New Zealand, where his second innings 47 helped save the game. He then made 74 against South Australia and an innings of 75 against the touring Indians saw him discussed as a potential future test player. He followed this up with his debut first class century, 140 against Victoria.

1981-82

Ritchie impressed again during the 1981-82 season with 55 and 71 against the touring West Indies, then the best team in the world. 126 and 103 against South Australia saw him discussed again as a test candidate.

Towards the end of the summer he was placed on stand by for Kim Hughes in Australia's one day team. He did not play in the end.

Ritchie was overlooked for the Australian tour to New Zealand in early 1982. However a century against Tasmania helped ensure his selection on the 1982 tour to Pakistan. Ritchie finished the season with 839 first class runs in ten games at an average of 59.

1982 Tour of Pakistan

The leading batsmen on the tour were Kim Hughes, Allan Border, Bruce Laird, John Dyson and Graeme Wood. Ritchie and Wayne Phillips were the two young batsmen. "They will be given every opportunity for the tests", said Hughes.

59 against the Pakistan Cricket Board XI impressed and Ritchie was picked to make his test debut. He scored 4 and 17. During the game he threw a stone at an umpire to demonstrate what was being thrown at him from the crowd.

Ritchie kept his spot in the side for the second test, although there was some talk he would be replaced by Peter Sleep. His maiden test century was the one bright spot of Australia's defeat. However he failed twice in the third test, making 26 and 18.

Ritchie was hit by projectiles while fielding at third man during the 3rd ODI, which was abandoned.

1982-83

Ritchie kept his place in the Australian team to play England in the first test. However also in the twelve was David Hookes who was in very good form. Despite 67 and 46 against Tasmania, Ritchie was made 12th man for the first test. Ritchie was picked in the side for the second test but was again made twelfth man. He was not picked in the squad for the remainder of the summer.

That summer was a disappointing one for Ritchie, despite 55 against Victoria.