The Boston Red Sox have rapidly discovered the most essential quality these Washington Nationals possess. They do not let up. They will throw Stephen Strasburg and a 19-year-old cyclone at you one night, and the next day the league's least hittable pitcher and most athletic infield will be waiting. They never let you catch your breath. They give no quarter.

It is the primary reason why the Nationals have the second-best record in the major leagues, and why they held on to beat the Red Sox, 4-2, at Fenway Park on Saturday afternoon. Gio Gonzalez backed up Strasburg's dominance with a gem of his own, allowing two runs in 61 / 3 innings on three hits and two walks. The dual brilliance that clinched a series victory has defined their season. The last two days, Strasburg and Gonzalez struck out 18 while allowing seven hits. The Nationals are 20-4 when Strasburg or Gonzalez start.

"Oh, I've heard it all year from other teams," first baseman Adam LaRoche said. "Guys get down to first and say there's absolutely no break in this rotation. And it can be a miserable feeling. You run into an offense that's struggling a little bit, and our staff definitely doesn't help."

Saturday, the Nationals' final 15 batters failed to reach base, but they produced enough offense off Red Sox starter Daisuke Matsuzaka, who made his season debut after undergoing Tommy John surgery. LaRoche clobbered his 10th homer of the season. Michael Morse drilled an RBI, ground-rule double. Ian Desmond smacked a game-breaking, two-run single.

The Nationals needed the cushion as Gonzalez faltered late and the Red Sox rallied. But for the most part Gonzalez dominated, rebounding from a rare clunker against the Atlanta Braves in his last start.