When the Padres fired Josh Byrnes on June 22, part of their rationale was to get a jump on other clubs that might seek to hire new general managers in the offseason. The Pads were onto something. Once the season ends, a number of organizations could experience shakeups in one form or another. The decisions of some clubs will hinge upon their finishes. But for other franchises, the die is all but cast. With less than 50 games remaining, here is a look at the potential upheavals. Phillies Phillies president David Montgomery is immensely loyal to his employees, but the team’s home attendance is cratering — from an average of at least 44,000 from 2009 to ’12 to 30,346 this season. The failure of general manager Ruben Amaro Jr. to make a single trade before the July 31 non-waiver deadline only intensified fan unrest. Amaro since has moved right-hander Roberto Hernandez. He can shop other players this offseason. But if not for Montgomery’s protection, Amaro might be gone by now.