Who -- or what -- can stop the Washington Nationals?

The first half was a breeze, but NL East-leading D.C. is no lock for second-half dominance. Here are some potential roadblocks en route to October.

It was a breeze of a first half for the Washington Nationals. As we emerge from the All-Star break, the Nats have a 9½-game lead in the NL East. Their .591 winning percentage is the fourth-best in baseball. Of the 102 days in the season, they've had at least a share of first place for 99, more than any team in the majors.That's not to say there's nothing to worry about in the second half. Here's a list of five things that could derail the Nats in their attempt to make the playoffs in back-to-...