The seeds of India's defeat were sown in Melbourne, where Bumrah had to bowl 53.2 overs -- 24.4 in the second innings on the back of 28.4 in the first innings.
With just three days to recover, that was an inhuman burden on a bowler who had bowled 151 overs in this series.
Morning session
Virat Kohli led the Indian team out onto the field this morning in the defense of a meagre target of 162. In the absence of Jasprit Bumrah, Mohammed Siraj led the attack; his first over went for 13 runs, including a waltz down the wicket by Sam Konstas to smear the ball over the infield to the mid on boundary.
It was the worst possible start to a defense of 162.
It didn't help that first Siraj, then Prasidh Krishna, in the respective first overs gave away four byes each with some wild bowling.
The two opening overs produced 26 runs -- and that was the game gone.
Konstas fell in the 4th over trying, and failing, to launch a Krishna delivery into geo-stationary orbit (22 off 17, Australia 39/1), but the muted celebration by the bowler and fielders underlined what everyone watching already knew, that the fielding side had started in sloppy fashion.
When Australia's 50 came up, in just the seventh over, India had conceded 14 extras -- five byes, eight wides, and a no ball. And that told you the story -- absent Bumrah, there was neither a plan, nor discipline, in the attack.
India's faint hope at start of play was for Ravindra Jadeja, the number six, and Washington Sundar, the batting allrounder at number eight, to add some significant runs. 40 would have been good, anything above that would have increased India's chances.
That hope didn't materialise. Pat Cummins in his second over found Jadeja's edge through to the 'keeper; he then pushed Washington back with a series of sharp short deliveries, then delivered the sucker punch in the form of a fuller length ball -- anticipating the short one, Washington pushed at it from deep in the crease and outer-edged onto his off stump.
At the other end, Scott Boland got Siraj edging to Usman Khawaja at first slip; then seamed one from off to leg to go under Bumrah's flailing bat and knock back leg stump to complete a six-for -- not numerically as impressive as the 6 for 7 he took on his debut, but in terms of this game and the outcome of the series, Boland was the difference with 21 wickets in just six innings, each wicket costing him a mere 13.19. To emphasise those figures, consider that Cummins' 25 wickets came in 10 innings, at 21.3.
From an Indian point of view, consider also that the three all-rounders -- Jadeja, Reddy and Sundar at six, seven and eight respectively -- who were brought in to 'strengthen the batting' scored 29 runs between them.
Marnus Labuschagne gifted Prasidh a second wicket when he carefully steered a short ball, from around 5th stump, straight to Yashasvi Jaiswal in the gully (6 off 20; Australia 52/2).
Smith was one short of 10,000 runs in Test cricket when got himself into that awkward tangle; Prasidh's ball rose on a line around 6th stump. The batsman fended, and was taken by a diving Jaiswal in the gully. (4 off 9, Australia 58/3, 104 still in deficit).
Two factors contributed to that dismissal. For one, Smith was walking towards the ball, both forward and across the stumps -- which meant that he was too close to a wide ball that, had he remained around off and on top of the crease, was an easy leave; for another, the uncharacteristically extreme bounce of the SCG meant that he had no way to avoid that ball. Remember Melbourne, where edges didn't carry to the slips? The bounce in Sydney made all the difference. Smith ended on 9,999 runs.
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Australia went in to lunch at 71/3. The session produced a remarkable seven wickets for 87 runs in 20.5 overs. Australia need another 91 runs with seven wickets standing -- and on balance, you have to say the home side looks good to seal the series 3-1, particularly with Bumrah ruled out.
The outside chance India has comes from the pitch, more than the bowling. The striations running the length of the pitch are more pronounced now, and when the ball hits one of those cracks, the bounce is extreme, and batting is not easy -- particularly because some of those cracks are close to good length, which means a batsman coming forward to length could get into a tangle as the ball climbs a ladder towards his face.
To take advantage of the conditions, the Indian bowlers needed to be a lot more disciplined in line -- ideally, on and just outside the stumps -- than they have been.
Siraj, with the burden of leading the attack thrust on him, has been anything but, bowling all lengths and lines and, as a result, leaking runs -- 38 of them in just seven overs.
Krishna, in six overs, has three for 27, and has given India a glimmering of hope. That two of his three wickets are due to rank bad batting by Labuschagne and Smith doesn't matter -- this series is about two underwhelming batting lineups competing to see which is worse, anyway.
But... Bumrah. Just how much do we miss him? And just how much does his Herculean effort in the fourth Test cost India now?
Post-lunch session
The seeds of India's defeat were sown in Melbourne, where Bumrah had to bowl 53.2 overs -- 24.4 in the second innings on the back of 28.4 in the first innings. With just three days to recover, that was an inhuman burden on a bowler whose action puts a huge strain on his body, and who by the time he broke down completely had bowled 151 overs in this series.
That moment when, called upon to bowl his eighth spell of the day, Bumrah went through an over at around 120k, then dropped his hands to his knee and said Ab bas, zor nahin mil raha hai, was the harbinger of what was to come.
The saddest sight of the day, from an Indian fan's perspective, was that of Bumrah in his whites, seated in the dressing room right next to Rohit Sharma, the two moodily watching as Australia progressed towards the target.
In one of those cruel ironies of sport, Bumrah, who had put India on the path to victory in Perth with an opening spell for the ages and who had kept India in the series till the fourth Test, could only look on as India surrendered its decade-long grasp on the Border Gavaskar Trophy.
Team selection did not help. As Prasidh Krishna and Mohammed Siraj continued after lunch, after bowling unchanged in the first session, the question loomed: Who takes over?
Nitish Reddy is the only seam option left. Nothing against the lad, but he is primarily a skiddy bowler operating in the low to mid 120s -- and on this wicket, variable bounce is what makes batting difficult.
And then you have Jadeja and Sundar who, in this entire series, have never had one spell of any significance. What would India, in the post lunch session, have given for one more quick bowler capable of utilising the devils in this wicket -- a Nitish Rana, say?
Batsmen have been blamed, rightly so, for India's plight -- but as always, the selectors and the coach get a free pass for what you could only call asinine team selections.
Bumrah's absence was particularly felt in the first fifteen minutes after lunch, when Usman Khawaja -- without the spectre of India's spearhead, who in previous Tests had taken the opener's wicket for fun -- unfurled a straight drive and a cover drive off Krishna, sandwiched around a rasping square cut off Siraj as the Indian quicks bowled both lengths in a search for quick wickets.
An airy waft at Siraj saw Khawaja nicking off -- but he had, by then, scored 41 off just 45 balls, way too many, in a low chase, from a batsman who had been a walking wicket till then. By the time he was out, the target had been reduced to 58, and the game was going only one way.
The 12 hours India bowled in the first hour after lunch produced 76 runs for the wicket of Khawaja -- drinks came on with Australia needing a mere 15 runs to win.
By the time India made its first bowling change, with Nitish Reddy replacing Krishna -- for just one over to allow Siraj to switch ends -- the two opening bowlers had sent down 21 overs in one uninterrupted spell on either side of lunch, for 112 runs and the four wickets they shared.
Travis Head, on the back of three successive failures, left his flashing horizontal bat in the hut and came out with a more cultured one.
Playing mostly with the straighter bat, the sticker pointing back down the pitch at the bowler, Head reined in his attacking impulses, and looked to rapid strike rotation -- a good ploy, because every single run pushed into the outfield was hurting the bowling side. That pressure forced the bowlers to try different lines -- and produced errors that Head cashed in with emphatic shots to the fence on both sides of the wicket.
Once Beau Webster, reprieved by DRS on an LBW appeal by Siraj because the impact was outside line of off, got into his stride and picked up where he had left off in the first innings, fours flowed from both ends and the game was done barring the song of the obese lady.
As Australia cruised home, the bowling figures made sorry reading. Sundar got his first over with Australia needing a mere 11 runs. Webster took him down for two successive fours, and it was all over.
In effect, two all-rounders taken to 'strengthen the batting' contributed nothing of significance; the batting was not strengthened, rather, the bowling was weakened immeasurably.
It took Australia just 27 overs to seal the deal. Travis Head, with 34 off 38, and Webster, with 39 off 34, remained unbeaten. The partnership was worth 58 off 53; the two not out batsmen had ten fours between them.
With the win, Australia have made it to the World Test Championship final, irrespective of results in the two Tests it will play against Sri Lanka. But I suspect that for Cummins and his team, winning the BGT will matter more.
Australia is an aging side, with one teenager and everyone else on the wrong side of 30. With this win, they now hold the trophy, or have won the most recent series, against every Test side they have played.
They are the defending world Test champions, the number one Test side. Beating India and winning the Border Gavaskar Trophy was the one remaining box Cummins and company wanted to tick to seal their legacy as one of the great Australian sides -- and that box has been ticked with an emphatic 3-1 margin.
Against that, India has now lost bilaterals against Sri Lanka, New Zealand, and Australia in the last 12 months and a week -- and before the next WTC cycle begins in England in June, they have questions to answer; questions that run the length of their lineup and take in the selectors, the coach, and the cricket administration.