There’s no question that in his early career Miller was seen predominantly as a batsman, and an outstanding one at that, nor is there any question that the demands of bowling – and of not taking anything particularly seriously – took the edge off his batting as his career progressed. Phillip Derriman put it best when he noted that “Miller came into big cricket as a brilliant batsman who surprised people by bowling as well as he did, and went out of it as a great fast bowler who could still bat brilliantly but only on occasion.“
For most people, Miller shone brightest as a batsman in 1945 in the Victory Tests and for the Dominions XI against England – in those six “Tests” he made 654 runs at 72 with four centuries and his batting was by all accounts of absolutely the highest class. Bill O’Reilly was one of many convinced he would go on to become one of Australia’s greatest ever batsmen but as Tiger himself later said: “He never blossomed out as I was certain he would.”
There are a number of reasons for this, and Bradman can take some credit/blame – he recognised in Miller early on a great natural bowler and the Australian side of the time needed Miller’s bowling more than his batting, so as Nugget’s career progressed bowling assumed the greater significance, even if his back problems meant that he couldn’t bowl the sheer quantity of overs that his captains might have liked. It should be remembered as well that due to the war Miller didn’t play his first Test until the age of 26, and was 27 by the time he played his second. It’s only natural then that he declined after a few years, given by that time he was well into his 30s.
It was noted too by John Warr among others that Miller’s technique, particularly on wet wickets or those taking spin, could be found wanting – too much pad and not enough bat, and without the patience required in those conditions to build a big score. As Ikki, Matt and several other posters have also correctly pointed out, Miller relished a contest and found it hard to motivate himself to cash in against minnows – it’s no coincidence that all of Miller’s Test centuries came against either England or WI, the two other major powers in world cricket at the time.
To say that he never performed with both bat and ball at the same time isn’t correct though. He’s one of only two men along with Sobers to score 300 runs and take 20 wickets in the same series more than once, and topped 200 runs/15 wickets in four further series. For a player renowned for flights of erratic behaviour and a devil-may-care attitude, his overall Test career is actually one of admirable consistency. Whether he would have achieved more or less with a different attitude is a moot point, what he did achieve still puts him among a tiny elite.