Mitchell Johnson runs up now, he bowls, it's angled across the right-hander, left alone outside the off stump, no run ...

So runs a description of a typical Johnson delivery, one that has been on offer all too often lately. When Johnson is in full flow, the delivery is interspersed with regular wickets, gained through pace, occasional swing and a vicious, armpit-seeking short ball. Presently, though, he is not in full flow, and is increasingly mired in the sort of Test-wicket drought that no one would want to endure, especially not as they near their 30th birthday.

Nine months have passed since Johnson caught lightning in a bottle in a Test match. At the time, his six first-innings wickets against England in Perth carried the whiff of a happy accident: having not swung the ball an inch in Brisbane, he was dropped for the second Test in Adelaide, before suddenly beginning to swerve it around corners. Regrettably, the next five Tests have proven that a freak event is precisely what it was. Across these matches, he has taken only 11 wickets at a cost of more than 50. When he walked off the WACA ground his bowling average was 29.00, it is now nudging 31.00. They are the sort of figures that get a bowler dropped, no matter how senior or potentially dangerous.

In subsequent Ashes jousts in Melbourne and Sydney, Johnson was taken for four an over as he struggled for swing or even basic direction. His last contribution to the series was to lose his bails first ball to Chris Tremlett, as the Barmy Army sang mockingly from the stands. Aiming to make amends, Johnson appeared to do all the right things in the off-season that followed. He chose to forsake the Twenty20 Big Bash League to concentrate on Test matches, trained hard in the nets, and developed a relationship with his new bowling coach Craig McDermott - the enigmatic Troy Cooley had moved on to the Centre of Excellence. Rested from the tour match that preceded the Tests, Johnson even swung the odd delivery on the practice pitches at P Sara Oval, McDermott collecting them watchfully in a baseball glove.

Yet, on the resumption of Test cricket against Sri Lank in Galle, Johnson's bowling seemed curiously muted. Though he was no less accurate than usual, and played his part as a member of the bowling ensemble that secured a meritorious victory on a difficult pitch, a certain spark was missing. Australia's fielding coach, Steve Rixon, had predicted that Johnson had the potential to run through the hosts on a pitch with uneven bounce, but he took only two wickets in the match. There was no swing discernible, even though Ryan Harris and Shane Watson gained enough to pose consistent problems for batsmen young and old.

The pattern has continued on less helpful strips in Pallekele and Colombo, as Sri Lanka played him with some care but also took advantage of plenty of opportunities to score. His only wicket so far at the SSC involved a meaty drive intercepted at short extra cover by Ricky Ponting: not exactly the bowled, lbw or slips catch he has seemed to be looking for. Johnson's offspinning slower ball is excellent, but even that could be delivered with more regularity, to provoke the sort of miscue that nearly ended the innings of Tillakaratne Dilshan on the third morning. By the afternoon he was being treated with some contempt by Angelo Mathews, and Ricky Ponting was offering frequent advice.

Why Johnson has struggled for wickets is a matter of debate. He has not swung the ball, but that has not stopped him from discomforting and dismissing batsmen in the past. He is not bowling with the greatest control, yet, there have been times when he has bowled far worse. Johnson's top pace here is around the 145kph mark, which is consistent with his upper register over the previous four years. And his mind and heart seem to be in the right space, as evidenced by a friendly, chatty visage across the tour.

Johnson's nadir took place during the first Ashes Test at Lord's in 2009. At the time he was expected to be Australia's best threat with the ball, yet over the course of that match he was the tourists' greatest liability. Dirty family laundry aired in the press did not help. Ever since he has worked at being at once tougher and happier, and also a little thicker-skinned. No such problems have been evident in 2011, and so cannot be considered central to his present torpor.

The answer, if there is one, may lie in the place where Johnson is most vulnerable - his bowling action. Johnson's method has always had something to it, but something missing as well. It is inherently difficult to judge how well Johnson is bowling, simply because his action does not exist in the easy space between instinct and training that most quality international bowlers inhabit. Save for days like that one in Perth, every ball can seem a battle, and Johnson is in the habit of holding up his left arm in subtle rehearsal immediately after most of his deliveries.

With the handicap of his technique, Johnson has often relied on the confluence of environmental factors for his most telling moments. He first emerged as an international bowler of note on a damp, humid night in Kuala Lumpur in 2006, skittling four India batsmen, including Rahul Dravid and Sachin Tendulkar, in a handful of overs. The planets aligned then, as they did again in Perth. When they will next is anybody's guess, not least the national selectors'. They must now decide how long is too long to wait between stand-out spells, and at the moment the gap is starting to yawn. One more series may be all he has left.

For the moment, the location of that series is a source of hope. Australia's next Test assignment is in South Africa. This, of course, was the scene of Johnson's most triumphant performances. In 2009 he swung the new ball and dished out blood and thunder, proving the ideal spearhead as the tourists enjoyed an unexpected 2-1 victory. The effort was striking for both its swing and its hostility, and the consensus was that Johnson had formally arrived. He has been coming and going ever since.