without a leg to stand on字面意思是没有了脚，也就是“站不住脚，无法取信于人”的意思。

【例句】
We don't feel we should have to listen to them anymore since they're without a leg to stand on.
他们说的话站不住脚，没资格教训我们，我们觉得我们不该再听他们的话了。

It seems the baseball 'hero' ended up without a leg to stand on.
于是，原来的棒球“英雄”最后似乎变得毫无可信性。