This would not be the first tripleheader in major league history:
"There are three recorded instances of a tripleheader in Major League Baseball, indicating three games between the same two teams on the same day. These occurred between the Brooklyn Bridegrooms and Pittsburgh Innocents on September 1, 1890 (Brooklyn won all three); between the Baltimore Orioles and Louisville Colonels on September 7, 1896 (Baltimore won all three); and between the Pittsburgh Pirates and Cincinnati Reds on October 2, 1920 (Cincinnati won two of the three). "
And a real triple-header is now forbidden by the Basic Agreement, anyway:
"Triple headers are now prohibited under the current collective bargaining agreement, except when the first game is the conclusion of a game suspended from a prior date. This would only happen in the extremely rare case of the only remaining dates between teams being doubleheaders and no single games are left for the suspended game to precede."
(Above from the Wikipedia article: Doubleheader (baseball).)
And, as the Mets have another series at home vs. the Braves this season in late July, there's no reason to play a triple header, or even double headers both on Tuesday and Wednesday.
