Jacob already explained what moneyball is its not always players up the leagues we need to compete for.

There could be players in leagues below us who have great stats it is finding them before others do.

You could argue Roberts is one who worked but possibly Knight wont work ?

Cameron more than likely had good stats at Torquay but he is more likely to have impressed whilst we scouted Torquay and played them.

No method is fool proof everyone signs good and bad players you just need a 60-70% hit ratio.