Mental strength is a major factor in cricket. Marshal Ayub has the courage to bat at #3 and riyad don't have. Even Mominul showed the courage to bat up. First Riyad lost the #4 now lost #3,and ultimately losing position from the team. If you are a good batsman u should bat up. Every time Riyad offered to bat up re has refused. Ultimately he is in the Bink of extinction.
From cricinfo: " According to sources, Mahmudullah, currently out
of favour in Test cricket, was asked whether he
would take over the No.3 role. He wasn't too keen,
it was learned. There were also thoughts of
promoting Mominul or sticking in Jahurul Islam, as
Anamul Haque would be opening the innings with
Tamim Iqbal."
http://www.espncricinfo.com/banglade...ry/680437.html