Originally Posted by beast of mallorca
It's actually yosh(i).
Yoshi is another alternative. There was a thief who shouts yossha after stealing a car. http://www.youtube.com/watch?v=rTbh4NOlQRQ
I also heard a Japanese player shout yossha and yoshi before as well. I would need to watch Japanese tennis videos on you youtube again to make sure because it has been a while since I watched a Japanese tennis match.
Shaa might be another alternative as well. I think I heard that in Prince Of Tennis.
Are you a native speaker or a N1, N2, or N3 level (Japanese Language Proficency Test)?