According to the DS, there's nothing wrong with Sunny physiologically. Apparently he is emotionally distraught over property related family issues. If the DS report turns out to be accurate, then it's a freaking shame for someone who's anything but a sissy with the ball.
Sunny's willingness to toss it up and go for wickets is admirable. Especially in light of the way many BC experts tend to conflate ODI style, flat and rifled, "containment" bowling with test bowling requiring 20 wickets to win a match. With Mushfique's defensive field setting, questionable bowler management and lapses in correctly assessing and responding to match situations - all observed during day 1 of Test 2 - someone like Sunny would've been immensely useful.
I hope Mushfique continues to rely on Shakib (should never have been stripped of the captaincy, as great as Mushfique is doing with the bat) and uses Rubel and Nasir more than a totally useless Shahadat and semi-useless Shubho, that good delivery notwithstanding. Nasir needs the freedom to toss it up and vary his length. If he already has that freedom but is choosing to play it safe, he needs to be motivated into going for wickets on account of his merit, and not unforced batting error. Shakib needs to set the example here.
None of this is easy on this crappy wicket.
"And do not curse those who call on other than GOD, lest they blaspheme and curse GOD, out of ignorance. We have adorned the works of every group in their eyes. Ultimately, they return to their Lord, then He informs them of everything they had done." (Qur'an 6:108)