(Pat Sullivan/AP)

Tonight, the Nationals will start to define more clearly what kind of team they are against reigning Cy Young winner Clayton Kershaw and the Los Angeles Dodgers, who have the second-best record in the National League at 13-6 and, in Matt Kemp, the very best player in baseball. The Nationals will receive a new kind of challenge at Dodgers Stadium, where the Dodgers have gone 7-2.

“I think you learn more about your ball club and the talent you’ve got by going up against the best, another club that’s playing the best,” Manager Davey Johnson said. “I’m looking forward to that.”

Few predicted tonight’s match-up would pit two first-place teams, let alone the two best records in the National League. The Nationals have surged behind historic starting pitching, becoming the first team since 1900 with eight scoreless starts in the season’s first 19 games.

The Dodgers have been stingy, too, with a 3.21 ERA. The main factor for them has been Kemp, who is playing on an entirely different level than anyone else in the majors. He leads the world in hitting, on-base percentage, slugging and home runs, and his 1.455 OPS is more than 250 points clear of the next closet.

“This will be a good test for us,” outfielder Jayson Werth said.

The Nationals have passed every other test this season, even losing by a single run in four of their five losses. They will send to the mound Ross Detwiler, who somehow has become the overlooked member of the Nationals’ rotation despite posting the best ERA, 0.56, in the majors. Both he and the Nationals will have their chance to make another statement tonight.