Tsip are a bit overrated or mental midgets. .
You are calling Perseus a mental midget! :lulz2:
Perseus has defeated all three members of Big Three. Moreover, he has beat Ralph on Clay and Fed in a Slam. Tell me how many players less than 25 have managed to defeat all members of Big Three (without even worrying about in which tourney or which surface they beat them).
Perseus had weak results in the second half of this year. But, I am sure he will bounce back next year.
In fact, my answer to the original question in the pool is Perseus. He will be the first one from this group to win a slam (I am excluding Thiem here due to his age).