Lucas Duda finally came through for the Mets with a solo homer off Drew Storen to lead off the seventh.
Gonzalez's only trouble came after he walked Mets catcher John Buck to open the second inning. Duda followed with a single, and Zach Lutz plated Buck with a sacrifice fly. The Mets mustered only three other hits against Gonzalez, one apiece by Marlon Byrd, Collin Cowgill and Ike Davis.
"I was trying my best to attack the strike zone," Gonzalez said. "I was giving [catcher Wilson Ramos] work behind the plate, and he was doing a great job behind the plate. But the defense was most important today -- guys were making great plays, double plays. Other than that, I'm still working. Arm feels good, just trying to build a little arm strength, that's all it is."
Returning to big league camp for a spot start, Montero was sharp over 4 2/3 innings, allowing four hits and a walk but no runs. He struck out three. Montero made the start because right-hander Shaun Marcum, who is due back next week, missed his most recent rotation turn with a right shoulder impingement.
Slated to break camp as a utilityman, Nationals third baseman Chad Tracy was the only Washington batter to provide any early offense, finishing 3-for-3 with a double. The Nats did not score until Francisco Soriano's sacrifice fly off Josh Edgin in the seventh. With the bases loaded and two outs, Edgin then struck out Jerad Head to escape further damage.
Up next: The Nats head back to Viera on Sunday to take on the rival Braves at Space Coast Stadium at 1:05 p.m. ET. Bryce Harper is expected to be back in the lineup after being scratched before Saturday's game, and Jordan Zimmermann gets the start against Atlanta right-hander Kris Medlen. The game will be broadcast live on MLB.TV, MASN and 106.7 FM in Washington.
Anthony DiComo is a reporter for MLB.com. Follow him on Twitter @AnthonyDicomo. This story was not subject to the approval of Major League Baseball or its clubs.