As the most successful England side in a generation fell apart in Australia 18-months or so ago, it seemed one man above all would prove almost impossible to replace.
It wasn't Andy Flower, the architect of England's golden era. It wasn't Jonathan Trott, whose batting had reassured for several years. It wasn't even Kevin Pietersen, who as recently as 2012 produced some of the greatest innings in England's Test history.
It was Graeme Swann.
Swann was the spinner who made the four-man attack work. Swann was the spinner who offered control in the first innings and a threat in the second. He was the catcher who made second slip his own. The lower-order batsman who defied his dislike for bouncers to produce many important innings. He was England's best spinner since Derek Underwood.
While Swann conceded his runs at rate of under three an over, his potential replacements, Simon Kerrigan and Scott Borthwick respectively, conceded theirs at rates of 6.62 and 6.30 respectively during chastening debuts. It appeared England had a serious problem.
But then they stumbled across
Moeen Ali. And, in his first year of international cricket, Moeen has done a remarkably good job of replacing Swann. His bowling average is actually better at present, albeit over a small sample size, and he has already made the Test century that eluded Swann.
Perhaps the expression "stumbled across" Moeen is unfair. England spotted something in Moeen's spin - and it was for his spin bowling that he was first selected for Test cricket - and were convinced to persevere with him despite an unconvincing first couple of Tests with the ball partly because of his batting. His century in his second Test at Headingley was an unusually fine innings.
There are echoes of the Swann story here. It was Peter Moores who called Swann into the England Test side and Moores who made the decision to give Moeen time to grow into the role. The amount of spin he imparts causes the ball to dip sharply, just like Swann, while his action creates drift that threatens both edges; again, just like Swann. It has proved an inspired selection.
Nobody is more surprised at Moeen's emergence as a spinner than Moeen. While he was never the part-timer that some claimed - he had taken 101 first-class wickets at 33 apiece since the start of 2012 before the Southampton Test in 2014 that changed his life - the speed of his improvement has been remarkable.
While many spinners find they need to bowl quicker to sustain a career at international level, actually doing it while maintaining control is another thing entirely. Just ask Adil Rashid. As Moeen put it after the Grenada Test: "My bowling has been a revelation to me."
They key to his improvement was spending time in and around the England squad. Bowling in the nets, Ian Bell suggested that, if he were to prosper at the top level, he would have to find a little more pace and bowl a more attacking off-stump line. Then, just before the Lord's Test,
a chance conversation with umpire Kumar Dharmasena provided the technical insight to achieve the improvement.
"He advised me to grab my pocket with my non-bowling arm after delivery to get more body into my action without losing flight," Moeen said. "I tried it for one ball and knew it would work immediately. It made a huge difference."
The results were as immediate as they were dramatic. After conceding his runs at a rate of 3.90 an over and taking his wickets at a cost of 54.71 for his first three Tests, since that session at Lord's Moeen has conceded 3.02 runs per over and taken his wickets at a cost of 15.66.
It is no surprise that Moeen looked rusty for much of the Grenada Test. He had bowled only 11 overs in red-ball cricket since September when he joined up with the Test squad following injury at the World Cup. Feeling the pressure of replacing James Tredwell, who had done an excellent job in the first innings in Antigua, Moeen produced a nervous performance with the ball in the first innings and ran himself out in somewhat dozy fashion.
"I was bowling well in the nets and felt like I was ready," Moeen said as he reflected on the first Test. "But the pressure of Test match cricket and bowling at good Test players was completely different.
"With James Tredwell having bowled so well in the first Test match, I wouldn't say there was pressure but I felt I needed to bowl well and probably forced it a little bit. I spoke to Peter Moores and Paul Farbrace and they just told me to relax and enjoy it and that's exactly what I did."
Amid the excitement of James Anderson's terrific spell with the second new ball on the final day, it went largely unnoticed, but Moeen also rediscovered his rhythm towards the end. While two of the three wickets he took in that spell were tailenders - although that is not always an area where England have shone - the other was a classic Moeen delivery: Denesh Ramdin defeated by sharp dip and playing across one. It is not just coincidence that England have now won the last four Tests in which Moeen has played.
But Moeen remains frustrated by his batting at Test level. He has, he believes, shown only glimpses of his ability to date and knows that an average of 28.60 is a poor return for one so talented.
"I still feel there's a lot more of my batting to come," he said. "I just haven't justified it. Adapting to Test cricket is not as easy as people make it out to be. Although the way Gary Ballance is batting is making it look very easy.
"But hopefully I can find my feet as a batter a bit more. I know I can do it. I've done it for Worcestershire many times before, so I just need to get the confidence back and really enjoy batting as well. I feel like it's round the corner."
He brushed aside the suggestion - the far-fetched suggestion - that he could be promoted to the top of the order for the Barbados Test. Replacing a man who helped post England's first century opening stand for two years is one thing; replacing him with a man averaging 28 in the middle-order - and a man who might be expected to bat 10 minutes after bowling 40 overs - quite another. Moeen has quite enough on his plate for now.
"If they ask me to open then I'll open," he said. "But if they want me to bat 11 then I'll bat 11. I don't really mind. As long as I'm playing for England then I'm happy."
As well he might be. The last year has been a fairytale for a young man who grew up wanting nothing more than to play cricket. Now, with bat and ball, he finds himself playing a pivotal role in all three formats for his national side.
"I feel very comfortable and settled in terms of me as a person around the guys," he said. "At first you're fresh to the squad and you don't know exactly what's going on and you're a bit shy.
"I've played a lot of games. More than I expected. And I feel I've developed as a player and as a spinner. It has been a great year."
George Dobell is a senior correspondent at ESPNcricinfo