Mathematically, leverage is based on the win expectancy work done by Keith Woolner in BP 2005 (read an explanation by Dan Fox here), and is defined as the change in the probability of winning the game from scoring (or allowing) one additional run in the current game situation divided by the change in probability from scoring (or allowing) one run at the start of the game.
Et tu, Tampa Bay?
Providing every team’s bullpen picture at a glance.
Sure, there might be better ways to construct bullpens than the way teams do it now, but change might not be as easy as you think.
Which relievers were added to or removed from the managerial circle of trust between April and September?
How did closer usage end up where it is now? And is it truly benefiting the game of baseball?