Around this time five years ago, Mashrafe Mortaza took one of his most significant decisions as Bangladesh captain. A day before their first ODI against India in 2015, he took a look at the pitch while walking to the dressing room to join his team-mates. The grassy top and rough texture underneath meant he wanted to play four front-line pace bowlers, an unfamiliar formation in Bangladesh cricket. Specifically, Mortaza wanted Mustafizur Rahman to make his ODI debut.
"I told [coach Chandika] Hathurusingha that Mustafiz's cutter is unique and it has an impact," Mortaza says. "It will trouble India. Shakib [Al Hasan] and Tamim [Iqbal] told me it's the right decision."
Mortaza had seen how Rahman, a skinny left-arm bowler, had troubled Bangladesh's best batsmen in the nets. He had debuted in a T20I against Pakistan earlier that year and Mortaza felt confident enough about him to give up the safety of the slow left-arm of Arafat Sunny - who had played in the 3-0 series win against Pakistan - to accommodate a bowler with a little more mystery.
"I told him [Hathurusingha] that Arafat Sunny bowled well against Pakistan, so if he ended up with 2 for 45 against India, while Mustafiz had a bad day and gave away 60 runs, would the 15 runs make a lot of difference?" Hathurusingha agreed.
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Within the week, Rahman's 13 wickets had helped Bangladesh clinch their maiden ODI series win over India, and catapulted him to stardom.
He followed it up with pivotal roles in ODI series wins over South Africa and Zimbabwe. He became the first Bangladeshi cricketer to feature in the ICC's ODI team of the year for 2015. Early the next year, he had a hand in a win in the Asia Cup T20 and a five-wicket haul in the World T20. He then bagged an IPL contract with Sunrisers Hyderabad worth almost US$200,000.
Rahman played a key role in the Sunrisers' maiden IPL trophy win and also finished with the tournament's Emerging Player award. He developed a couple of fine yorkers during the tournament, in addition to his trusty offcutter.
In an early interview he said that he understood a slower ball could be delivered like a spinner's stock delivery, with the wrist and fingers putting action on the ball, so he copied the basic left-arm spinner's delivery that spun the ball out, but delivered it with a bit more pace. It was simple enough thinking, but it confounded many batsmen in those first 12 months. In the only Test he played in that period, against South Africa, he took a four-wicket haul, three of those wickets coming in the space of four balls.
Rahman is now struggling to produce his slower ball or offcutter out of the back of the wrist, which once made him a different bowler altogether
Then came a bump in the road: a shoulder injury in 2016 cut his time at England's T20 Blast short and eventually kept him out of action for five months. There was talk within the Bangladesh set-up that he had taken on too much cricket, and in hindsight the injury now marks a clear dividing line in his career so far.
In 22 white-ball internationals before the injury, he took 48 wickets at an average of 13.08 and a strike rate of 15.8; in the first games after his return, in December 2016, he took 32 wickets at double that average and strike rate. In the IPL, he took 17 wickets at 24.76 with an economy of 6.90 in his first season but for Mumbai Indians in the 2018 campaign, he managed only seven wickets at 32.85 and conceded nearly 1.5 runs more per over.
Clearly something wasn't right. Those who worked with Rahman closely could see it. He was struggling to bring out his slower ball, or the offcutter, out of the back of the wrist, the weapon that had once made him a different bowler altogether. He is far from finished, as evidenced in the 2019 World Cup, where he was among only four bowlers to take 20 wickets. But his franchise T20 career has stalled after the BCB accused him of hiding the seriousness of an injury, and he hasn't been able to crack Test cricket.
Mortaza still believes in Rahman, but not everyone sees him, or his unique cutter, in the same light these days.
Back in 2015, Mortaza and Hathurusingha had begun to think about tailoring home pitches to suit fast bowling, which would have represented a cultural shift in Bangladesh's thinking. Mortaza believed the likes of Taskin Ahmed, Rubel Hossain and Al-Amin Hossain were long-term pace prospects after they impressed at the 2015 World Cup in Australia. For a while, and after the addition of Rahman, Mortaza was right. But ultimately problems with the fitness and form of personnel scuppered the plan, and just over a year later Mushfiqur Rahim and Hathurusingha rolled it back: to beat teams like England and Australia at home, in Tests, relying on spin seemed the best bet again.
Since October 2016, Bangladesh's fast bowlers have bowled only 15.5% of the total 1871 overs the team has bowled in Tests on home soil, and taken just 19 of 220 wickets. The combined home bowling average for fast bowlers is nearly twice that of the spinners - 46.84 to the spinners' 24.04. The need for pace is greater in away Tests, but since Bangladesh play more at home than abroad, the quick bowlers' lack of volume at home restricts their progress.
That has had an impact on Rahman, especially as his debut Test hinted at red-ball potential. In that match he removed Hashim Amla, JP Duminy and Quinton de Kock in the space of four deliveries with a ball that was 59 overs old. All three deliveries were in the mid-130kph range; Amla poked at one that was angling away, Duminy was lbw to a cutter, and de Kock was bowled by one that kept low. There was clear potential for Rahman to be more than just a white-ball specialist.
After his shoulder injury, he was initially rested for three Tests so that he could build up to bowling large volumes. Eight wickets in the 2017 series against Sri Lanka was an encouraging sign, but in the years since, a combination of lack of bowling in home Tests, minor niggles, and what was perceived as Rahman's excessive eagerness to play in the IPL in 2018, left his red-ball future unclear, so much so that, ahead of Bangladesh's one-off Test against Zimbabwe in February this year, coach Russell Domingo had to clarify why Rahman, who had not played Tests for nearly a year - his last Test appearance was against New Zealand in 2019 - was in the squad.
"I don't think he is ready for Tests until he does some technical work so that it allows him to swing the ball back into the right-hander," Domingo said at that press conference in Dhaka. "Getting him back into the squad is the start of that process where he can spend some time with our new bowling coach [Ottis Gibson]. He was put back into the squad not to play but to train and get some shape back. He is going to be bowling every day, and I have told him that, to make sure that he gets into the shape that's required, as that benefits him in Tests and white-ball cricket." It turned out Gibson had asked Domingo to bring Rahman back, and he worked hard with him at every interval during the Test.
"He started to swing the ball back in," Gibson says. "I remember the first ODI against Zimbabwe in Sylhet, he had a really good lbw shout in the first over. The ball swung back in but he didn't appeal with any real conviction and umpire Kumar Dharmasena said not out. But when you look back at the footage, it was out. The ball had clearly come back in, so that's the start of it.
"Any team would love to have a left-arm fast bowler of his quality. He has the potential to learn and evolve to become a better bowler "Ottis Gibson, Bangladesh bowling coach
"I think he knows from experience what he needs to do in Test cricket. Of course, he has to do more than just get the ball across the right-handed batsman and bowl cutters. It won't be as effective. Russell rightly suggested that he needs to swing the ball."
After becoming the Bangladesh coach last August and linking up with new Test captain, Mominul Haque, Domingo has had to focus on building Abu Jayed and Ebadot Hossain as pace options for Tests, and wondering about newer options in T20Is, just in case.
But Gibson and he cannot afford to give up on Rahman, not with the current crop of fast bowlers Bangladesh have. Jayed and Rahman are the only fast bowlers to have a sub-50 average among those who have bowled in at least five innings. And Domingo has publicly said he wants to do away with Bangladesh's spin strategy at home and move to pace.
The impact of Rahman's shoulder injury is difficult to downplay, especially as it was likely a result of too much cricket. What if he had been less enthusiastic about franchise T20 leagues at the start of his career? What if he had skipped the T20 Blast soon after his IPL stint in 2016, when his body was already showing signs of strain?
That cutter, so lethal, was partly what brought on the shoulder trouble in the first place, given the pressure it exerted on one particular part as he wound his delivery arm around, with the wrist cocking at the last moment before delivery. His awareness of that, according to some, is what has made him hesitant about bowling that delivery since his return.
"That shoulder injury really did play a big role," said Heath Streak, Bangladesh's bowling coach between 2014 and 2016. "I think the mobility in his shoulder for his real big cutter has been affected. It is a huge weapon for him. I think this is the catalyst for him not going as well as he did in his initial stages. I think, also, people investigate ways to play [a bowler]. Batsmen have worked out better ways to play him, and maybe play him a bit more defensively."
The second point was first made as far back as that 2015 India series by R Ashwin, who had said then that the challenge for Rahman was only beginning, as batsmen began to decipher him.
Ajantha Mendis, the mystery bowler who left some of the world's best batsmen dumbfounded in 2008, is a valid reference point. Mendis was seen as the next big thing to come out of Sri Lanka, especially at a time when Muttiah Muralitharan's career was winding down.
But his brand of spin required stronger fingers and drier cricket balls, and as soon as batting line-ups figured out how to deal with him, Mendis' days were numbered. Despite a glorious start in 2008, he played his last international match in December 2015. His is the cautionary tale that should most worry Rahman.
For now, Rahman has time. But coming up on five years in international cricket should serve as a reminder of the ever-growing need to reinvent and develop himself.
"Fizz has had success in the shorter format but he also has to understand that having success in Test cricket requires a slightly different mindset," Gibson said. "You need to be a lot more patient, to be able to bowl the same ball over after over.
"Can you build enough pressure first and attack later? Do you have wicket-taking options with the new ball, in the middle of the game, and maybe when the ball is reversing? Those are the things that Fizz has to work out.
"I still think he has a part to play for Bangladesh. Any team would love to have a left-arm fast bowler of his quality. He has the potential to learn and evolve to become a better bowler than he is right now."
Rahman will need to prove when he trains with Gibson next that he is willing and able to make that effort. And he will know well that unlike with contemporaries like Kagiso Rabada and Jasprit Bumrah, who made their debuts around the same time and have the advantage of a cricket culture conducive - or increasingly so - to fast bowling, his circumstances are the opposite. He is seen as a quick bowler in a country where, at every level, pace bowling is only a filler.
Five years ago, Mortaza made room for him and Rahman didn't disappoint. Now, with Mortaza on the periphery and a head coach leaning towards pace again, it is the perfect time for Rahman 2.0.
Mohammad Isam is ESPNcricinfo's Bangladesh correspondent. @isam84