Michael Morse hit a grand slam, Bryce Harper also homered and the Washington Nationals became the latest team to tag a struggling Johan Santana in their 6-4 victory over the New York Mets on Friday night.

Ross Detwiler tossed six solid innings and the Nationals sent Santana to his fifth loss in the last five starts.

Handed a 2-0 lead, the two-time Cy Young Award winner was perfect through three innings. But the NL East leaders strung together four consecutive hits in the fourth, capped by Morse's 12th homer.

Harper, coming off a 3-for-32 road trip, turned on a fastball in the fifth for a two-run shot.

The Nationals, who have the best record in baseball, returned home following an 8-2 trip and have won 10 of 12 overall.

Washington began the day four games ahead of second-place Atlanta.

(Copyright 2012 by The Associated Press.  All Rights Reserved.)