he's the only optioned infielder on the 40-man roster. as mentioned in this thread, that's a severe lack of depth. rivera's burning his final option this year, and the because the brewers have been inclined to carry a 13-man pitching staff for most of the season, there really hasn't been any room for a guy out of options to keep on the 25-man roster (i.e. ivan de jesus, jr.). thus, any other infielder in the brewers organization added to the 40-man roster would most likely have be optioned, and if spending more than 20 days optioned, would burn that option. no reason to swap another guy now for yadiel rivera (although at this point, the brewers could outright rivera today, add dubon to the 40-man, option him, and recall dubon in september--well before the 20 days are up).