There was this guy in Pakistan cricket named Aftab Balouch, many years back who had the making s of a great batsman. He played a magical innings of 400 plus in the domestic cricket but then got hit on the head by a bouncer, and was never the same again.
As for Parsanna, I had the chance to skim through Miandad's autobiography (which is both interesting, and whimsical, just like the man himself), and he related that on that famous Indian tour to Pakistan, when the trio of Parsanna, Chandra and Bedi came in with a formidable reputation, the Pakistani batsmen found Parsanna the easiest to play (and Chandra the most difficult). Zaheer who was the senior batsman then compared with Javed, would tell Javed to give him as much strike against Parsanna, as he was looking to make big scores.