I've recently started playing Final Fantasy X again, after many years. One thing I always wondered about is the Besaid Aurochs player Botta. Every time you speak with him he says something like, "I don't want to be a burden," and I also remember a scene where Wakka looked at Bottza like, "Don't say anything, you know you screwed up". I haven't found anything online about him. Is there any source that says something about the history of the players and what may have happened between them?
According to this site, which appears to have a complete listing of the game script (or nearly so), the only possibly relevant dialogue from Botta* is comes when the team is preparing for their match in Luca:
Botta: Only five players in the sphere pool, ya? Which one of us is warmin’ the bench?
Botta: So, who’s warmin’ the bench? Could it be me?
Botta: A-Am I on the bench?
These are all solely in reference to the fact that, with the addition of Tidus, the team now has three forwards, so Botta is concerned with whether he is going to get to play.
*Since your question originally gave Botta's name as "Bottz," I presume that you are not playing on the English version, but in some other language, probably German, as Valorum points out. As a result, the quotes you encountered may actually represent a problem with the translation.