There is one measure by which the surprising, first-place Mets trail the disappointing Washington Nationals: talk.

As the Mets have taken the National League East lead, the Nationals—the overwhelming division favorites entering the season—have gotten unusually chatty about the competition. Last week, after a loss that dropped Washington into second place, Nationals star Bryce Harper said he doesn’t “give a crap about what the Mets are doing.” The next day, teammate Jayson Werth went further, telling local reporters that “it’s...