Who's indispensable to his team's postseason chances?

As we head toward the second half and the trade deadline, the teams with the most incentive to make a splash are those living on the margins, with their playoff fates in doubt. Manny Machado is a no-doubt-about-it superstar, but in the context of losing him to an injury or being kidnapped by aliens, the loss of Machado is essentially meaningless to Baltimore's playoff hopes.

It's the same three teams on top of the rankings -- Astros, Yankees, Red Sox -- but which is No. 1? And is another AL team ready to join them as one of baseball's best?

When healthy, Vladimir Guerrero Jr. has shown that he is ready to rake at the plate. We project what he and other top prospects can contribute in the…