Everyone loves a good story, and baseball is more than happy to oblige, providing those willing to listen with more than a few intriguing storylines from year to year.
MLB's storylines tend to change as the season rolls along, though, keeping baseball fans on their toes, constantly changing the focus of their gaze. What we once considered to be a must-follow story—say Derek Jeter's retirement tour—winds up being replaced with a more interesting and wide-ranging narrative.
What makes one story more interesting than another? Two things: impact and staying power.
Will we still be talking about this story a month from now, or is it something that we'll lose interest in in a matter of weeks? Additionally, does the story have a wide-ranging impact, one that affects a divisional race or an entire league's playoff picture? Does it involve a figure who is iconic enough that fans of other teams will have a genuine interest in him?
The 20 storylines that follow meet at least one of those criteria—and are the biggest in the game as MLB heads into the second half of its regular season.