Upon closer inspection, I decided that it was Kaidoh hitting the Boomerang Snake. He crouches way down to hit, the same blue racquet appears here and in the very next shot, which is Kaidoh hitting the Boomerang, the vapour trail on the court matches between the two shots, and, of course, no socks. But it is part of a montage of special shots, so it's hard to be absolutely certain. What do you think?
ETA further evidence in favour of Kaidoh: later in the trailer, Ryoma hits the Boomerang Snake too and he also drags the racquet on the ground first. Okay, I have no more doubts.
Horio, with two years tennis experience
If it's not Atobe, then who cares?