If you put a bad apple in a bushel of good apples, the bad apple won’t become good. In fact, when a bad apple starts to rot, it emits a gas that can indeed start to rot the good apples. But even if the bad doesn't completely rot the good apples, it's important to lock on to the fact that the bad won't get better by being with the good.
This is true with apples and true with sales talent. I work with sales leaders to help them figure out how to improve sales performance. I find that, too often, sales leaders are willing to accept a few bad apples on their team, thinking that they'll get better because they are mixed in with several good apples. This is simply not the case.
I saw this in action with a client I am working with now. This client got off to a rough start in 2017, but finished the year very strong. In the first half of the year, they were allowing a few bad apples to stay on the team and it cost them in performance. They made the right moves through the year and with a stronger team, they are delivering stronger performance.