He delivered the ball from a two-fingered grip at close to medium pace with great accuracy, and could produce leg breaks, googlies, and top spinners, with no discernible change in his action.

[1] A tall man for a spinner (around 188 cm, 6 ft 2 in), he whirled his arms to an unusual extent and had a low point of delivery that meant it was very difficult for the batsman to read the flight of the ball out of his hand.

His bowling action was far from the classic leg spin bowler's run-up and delivery, indeed, according to Wisden, "he was asked to make up the numbers in a Sydney junior match and, with a method that at first made everyone giggle, whipped out the opposition".

[30] O'Reilly did not enjoy his time at the overcrowded Sydney Teachers College (STC), decrying the lack of practical training and the predominance of pedagogical theory.

Regarding it as a waste of time, he happily accepted an offer of work experience from Major Cook-Russell, the head of physical education at STC, to help at Naremburn College instead of attending lectures.

Within half a dozen games, he was one of several young players introduced to the Australian cricket team for the Fourth Test in a badly one-sided series against South Africa.

The reprieved leg spinner took a total of 8/204 in his next two matches, and while the figures were not overwhelming, they were enough to ensure a Test berth; with an unassailable 3–0 lead, the selectors wanted to blood new players.

[50] The Australian selectors perceived that O'Reilly would be their key bowler, and as he had never played against the English, omitted him from the early tour matches so that the tourists would not be able to decode his variations.

The hosts were bombarded with short-pitched bowling and heavily beaten by an innings; O'Reilly took 4/86 as the visitors amassed 530, dismissing leading English batsman Wally Hammond in the first of many battles between the pair.

[54] After Australia had made only 228, O'Reilly trapped Bob Wyatt leg before wicket (lbw) before bowling both the Nawab of Pataudi and Maurice Leyland to leave England at 4/98.

[50][58] O'Reilly took 2/83 and 4/79 in Adelaide, collecting the wicket of Sutcliffe for single figures in the first innings of a match overshadowed by near-riots after captain Bill Woodfull was struck in the heart.

[60] The final Test in Sydney took a similar course; O'Reilly took 4/111 in the first innings including Sutcliffe and Jardine again, as the tourists took a 14-run lead before completing an eight-wicket win after another Australian collapse.

[63] Given his heavy workload in the previous season, it was decided to keep O'Reilly fresh for the subsequent tour of England, so he played in only two of the last three matches, with a reduced bowling load, taking eight wickets.

When O'Reilly came in at 8/273, only 17 runs were needed to avoid the follow on, but he misjudged the flight of a Hedley Verity delivery and was bowled, thinking the ball to be fuller than it was and missing a lofted drive.

O'Reilly always regretted his dismissal, as he believed that if he had helped to avoid the follow on, he would have taken "six wickets without removing his waistcoat" and that Australia could have then chased the target in better conditions on the fourth day.

[88] However, he almost failed to take to the field; O'Reilly and several players had threatened to withdraw after vice-captain Stan McCabe's wife was forbidden from sitting in the Members' Stand in the First Test.

Morris Sievers, from fewer matches, outperformed his average; Leslie Fleetwood-Smith, a slow left-arm spinner, got more eye-catching individual figures, including 10 wickets in the victory at Adelaide.

[37] In an otherwise high-scoring series, O'Reilly's greatest triumph was in the low-scoring Fourth Test at Headingley, where he exploited a difficult pitch to take five wickets in each innings as Australia secured the victory that enabled them to retain the Ashes.

O'Reilly effort proved to be crucial as Australia scraped home by five wickets just 30 minutes before black clouds brought heavy rain, which would have made batting treacherous.

In a timeless match, Len Hutton made a world record Test score of 364 in a fastidious and watchful innings of 13 hours, surpassing Bradman's 334.

[103] O'Reilly scaled back his participation in Sheffield Shield cricket in the 1938–39 season, making himself unavailable for most of the campaign to spend time with his newborn son after half a year in England;[104] he played in only two matches, against South Australia and arch-rivals Victoria.

[37] First-class cricket was ended after one match in 1941–42; O'Reilly took a total of 9/124 in a loss to Queensland[37] before the attack on Pearl Harbor signaled the start of World War II in the Pacific.

[117] In the late 1930s, the Australian Board of Control summoned O'Reilly, Stan McCabe, Leo O'Brien and Chuck Fleetwood-Smith, all Catholics of Irish descent to a meeting to discuss the apparent schism in the team.

[124] Despite their conflicts, a few years before his death O'Reilly wrote that, compared with Bradman, batsmen like Greg Chappell and Allan Border were mere "child's play".

[126] O'Reilly continued to work as a school teacher after he broke into international cricket, but at the end of 1934, after missing more than six months of the year in England, he resigned from his government post, reasoning that his career could not progress if he was going to be overseas so often.

The Premier of New South Wales, Bertram Stevens, tried to coax O'Reilly into staying in the government education system, offering him a post at Sydney Boys High School if he returned to STC to complete the Bachelor of Arts that he had abandoned a decade before.

[127] In 1939 he took a job in the sports store of close friend, teammate and fellow Irish Catholic Stan McCabe, which was located on George Street, the city centre's main thoroughfare.

He was held in high regard and granted full paid leave when he thrice went overseas for six months to cover tours of England as a journalist.

[137] His style was described by Wisden as "muscular, very Australian... flavoured with wit and imagery ('You can smell the gum-leaves off him', he wrote of one country boy just starting with Queensland).

[16][145] Upon retiring from The Sydney Morning Herald, O'Reilly wrote in a column As a writer on the game it has always been my one consuming resolve to tell my readers…exactly what my personal reactions were to the events of the day.