Shaheen Afridi toyed with Shadman Islam. He got him to jump around the crease and then sent him out with a full delivery that rammed into his pads.

Hasan Ali got one to scissor between debutant Mahmudul Hasan Joy's defence. Then, he had Bangladesh's captain Mominul Haque, with a full and fast delivery he couldn't get bat to.

Having roughed Bangladesh up with full deliveries, Afridi then adopted the short-ball trick to great effect as Najmul Hossain Shanto lobbed a simple catch to one of the two gullies stationed for just that.

On the fifth morning of the second Test, Bangladesh's top four were dismissed in no time after they had been asked to follow-on. And it's Pakistan's takedown of their brittle line-up in each of the four innings this series that was crucial to the 2-0 sweep.

The 7.62 Bangladesh's top-four batters averaged is the worst when they have batted in at least 16 innings in a Test series. Yet, all considered, they were about 20 minutes away from securing a draw, mainly due to Shakib Al Hasan and the lower-order resistance - and all the time lost to the weather earlier. But when the top four cave in as easily as they have, it doesn't help.

What contributed most to the top four's meltdown was Mominul having his worst Test series to date. He made only 14 runs, the least he has scored in any series in which he batted at least four innings. His previous lowest across four innings was the 94 he made against England in 2016.

Shadman, Mahmudul, the uncapped Mohammed Naim and Fazle Mahmud are the opening options in New Zealand. Can they cope with the green in New Zealand? Against Trent Boult, Kyle Jamieson, Tim Southee and Neil Wagner? It will be tough, that's for sure.

While the top four have been poor, it's also important to factor in their inexperience. Shadman and Shanto are playing their tenth and 11th Tests respectively, while Saif Hassan, who missed the Dhaka Test because of a fever, is just working his way up having made his debut last year. Mahmudul, meanwhile, is an absolute rookie.

They are all considered to be in the list of the country's next-in-line batters, who have all made at least one century in the season's first-class tournament. But how much is that really worth?

In Chattogram, Russell Domingo had said that the domestic structure doesn't prepare young players to make the transition to the highest level. It was a bold statement from a coach, who himself has often found himself at odds with the board bigwigs. "There's some exciting young players coming through but they are a long way off from where they need to be as international batsmen and bowlers," Domingo had said. "The more cricket they play at the domestic level or 'A' team tours, the better will be for the national side.

"Right now, the step up from domestic to international cricket is a massive step. It is something BCB needs to look at to make sure they impact the game and not take a long time to find their feet."

What would be most worrying for Domingo - and other stakeholders of the game in Bangladesh - going into the New Zealand series is the number of balls that the top four have faced in this series. It is the lowest for Bangladesh when they have batted at least 16 innings in a Test series, roughly one-third of the 854 balls that they face on average in a home series.

It's clear they aren't the same side without Tamim Iqbal, who scored four Test half-centuries in a row this year. His attacking salvo derailed Sri Lanka a couple of times in the Test series in April. Since his debut in 2008, Tamim is the fourth-highest scorer among Test openers. It's an understatement when we say Saif, Shadman and the new lot of batters coming in have big boots to fill.

Tamim is still a while away from returning to competitive cricket - he has multiple fractures in his thumb - which means Shadman, Mahmudul, the uncapped Mohammed Naim and Fazle Mahmud are the opening options in New Zealand. Can they cope with the green in New Zealand? Against Trent Boult, Kyle Jamieson, Tim Southee and Neil Wagner? It will be tough, that's for sure.

Mohammad Isam is ESPNcricinfo's Bangladesh correspondent. @isam84