Fletcher reckons the lowly Tigers could cause some problems if England sell them short at Lord's.

"They are a side that will make some progress. Cricket is a strange game and you can never underestimate anyone.

"It's important we appreciate there are some good players in their side," Fletcher told BBC Sport.

"There have been other sides who have been in the same position when they've entered the international arena and look where they are today.

"On any given day if one or two of their bowlers bowl in the right areas, you've got to make sure you're at the top of your game.

"We've got to make sure we go out there and play and look after own game and get some momentum going into the Ashes."

The England coach gave his backing to Ian Bell, who will make his second Test appearance after seeing off opposition from Robert Key and Kevin Pietersen.

Bell's place in the team is now his to lose, and he knows a strong showing against Bangladesh will put him in the box seat for an Ashes berth.

Fletcher scoffed at suggestions Bell would be ill-prepared to face Australia, saying his debut 70 against West Indies last year proved he could play at a high level.

"He has already done it against West Indies," Fletcher argued.

"It's not as if he's just come in and is totally new, which could mislead you to some extent.

"I think selection is showing that skill of not picking just on performance, but by seeing something in an individual, doing some investigation on his background and character and seeing if he can grow.

"We wouldn't pick someone just because he has made a few runs over a short period of time.

"He made runs last season, he's made some runs this season and Bell's a good player."

Fletcher was confident Andrew Flintoff would take on bowling duties at Lord's with his rehabilitation from ankle surgery going so well.

The star all-rounder has impressed in a number of spells for Lancashire this season, allaying early fears he would miss the Bangladesh contests.

"His progress has come on very well," Fletcher said.

"We had a chat with him the other day in Manchester and he gave the impression he would be disappointed if he didn't play.

"We must restrict the bowling that he does do, but he must build up mileage in his legs.

"He's all about power, there's no real rhythm in his action so he must make sure there's a slow, steady build-up.

"But he is up for it and enjoying his cricket. There is a lot of energy with Andrew Flintoff at the moment."