Some of the challenges Bangladesh will face over the next week in the one-dayers will be their bowlers' vulnerability in the death overs and Rubel Hossain's skills with the new ball.

In his last few years at the international level, Rubel has struggled with the new ball. In the just-concluded Test series, he picked up just one wicket, that of the nightwatchman Bruce Martin caught behind trying to pull a short ball. Though it was with a 10-over old second new ball, it wasn't what a fast bowler would be too proud of. His performance with the new white ball, however, has improved after he was smashed by Sri Lanka in Hambantota earlier this year, and an ordinary England tour for Bangladesh A. Over the last three years, Rubel has conceded less than four runs an over in six one-day matches (List A included).

In early October, he led the wicket charts in the ongoing Dhaka Premier Division, picking up all his 19 wickets for Gazi Tank opening the bowling. This change in form, although not reflected in his Test performance, has shown coach Shane Jurgensen a different side to his personality.

"I have picked up on a different Rubel," Jurgensen told ESPNcricinfo. "He is more confident now. His next challenge is to work on the new ball. He also has to work on his lengths. Like Lasith Malinga - and I am not saying that because their actions are a little similar - he has to challenge the batsmen full rather than short. He has the extra pace and is definitely worth persisting with.

"Rubel was very good with the old ball in both Tests. He was very unlucky not to get wickets. There were edges that didn't go to hand, went between the wicketkeeper and slips. I am definitely not satisfied (with his new-ball bowling). We need more work in this area."

Jurgensen is also worried about Bangladesh's death bowling. Off late, Rubel's old-ball skills have worked in containing the batsmen but the captain Mushfiqur Rahim has had to rely on the spinners in the last few overs. The plan this year during the off season was to make the fast bowlers fit enough to last 50 overs, in case they are asked to bowl at the death.

"With the two new balls, you have to think about the balance of your side a little bit more. We have done a lot of work on their fitness, so our plan is for the fitness to take them through the 50 overs," Jurgensen said.

"There have been times, at the death, when we haven't executed and it has cost us matches. Our big challenge in this series is whether we can execute at the death. It will carry into the other areas of our game as well."

But Jurgensen is hopeful that the spin attack, particularly Shakib Al Hasan, can continue to be on top of their game. Shakib took a five-wicket haul in the second Test in Dhaka, his first since December 2011. He has also guided Sohag Gazi in the absence of spin bowling consultant Saqlain Mushtaq. Although Abdur Razzak couldn't get much out of the placid wickets in Chittagong and Mirpur, Jurgensen praised their attitude.

"Shakib's bowling was a really fantastic sign. He just looked switched on. In your key game, you would want your best players up for the challenge. He hardly bowled a bad ball. It is great to have Razzak on, because of his leadership skills on and off the field.

"We didn't have the support of Saqlain Mushtaq this time, but I think that has created an opportunity for them, as a bowling group, to step up. You can have all the coaches in the world, you have to improve every day you train and play. Razzak always tries to get better," he said.

Mohammad Isam is ESPNcricinfo's Bangladesh correspondent. He tweets here