In the end, another K.

Plenty more in the middle, too.

A freight train confidently conducted by Stephen Strasburg rolled over the Red Sox in his first career start at Fenway Friday night. As he passed, there were many slow, dumbfounded walks back to the Boston dugout.

Beginning with Daniel Nava in the first and ending with Kevin Youkilis in the sixth, Strasburg fanned 13 with an arsenal of unhittable pitches, most of which the Sox futilely swung and missed at anyhow.

Sure, Strasburg had dominated before. He entered the game ranked third in Major League Baseball with 10.9 strikeouts per nine innings. Friday’s start was his fifth double-digit strikeout game this season, resulting in a 7-4 win.

Strasburg, who underwent Tommy John surgery in 2010, saved his gutsiest effort for his final frame.

Holding a 7-2 lead and already deep into a pitch count that wound up at a career-high 119, Strasburg loaded the bases with one out in the sixth. But the 23-year-old righthander set down Jarrod Saltalamacchia swinging and, with a 3-and-2 count, Youkilis looking at a 96-mile-per-hour fastball that got the Sox third baseman ejected for arguing about the pitch’s location.

“I don’t care what his pitch count was,’’ Nationals manager Davey Johnson said. “I was going to have to fight ownership if I let him go too long. But I didn’t want to have to fight Stras if I took him out.

“With his runners on there, in a game he was pitching, there was no way I was going to hook him.’’

The visit to Fenway came exactly two years after his ballyhooed major-league debut against visiting Pittsburgh, a game in which he struck out 14 batters. In his 12 starts that first season, he never once cleared 99 pitches.

“Obviously you don’t want to go out there and throw that many pitches through six innings,’’ Strasburg said after improving to 7-1. “But sometimes, they’re just going to make you work.

“Early on, they were taking a lot of pitches. That’s just where I need to do a better job of pounding the strike zone, making them swing the bat.’’

Not that he had any problems in that department.

Mixing a sharp curveball in the lower 80s, a fastball that escalated into triple digits the first inning, and a devastating changeup thrown at a speed some pitchers would enjoy having as a top velocity, Strasburg fanned 11 batters swinging.

Strasburg took some time getting into a rhythm. He walked David Ortiz to lead off the second and ceded a two-run double to Mike Aviles off the Green Monster that put the Sox up 2-0.

After Aviles’s double? Eleven straight outs, eight of them strikeouts, including a fourth inning in which Ortiz, Saltalamacchia, and Youkilis all went down swinging at curveballs.

“I have a tendency to almost try and throw a two-strike curveball in the dirt, not really trust it,’’ Strasburg said. “That’s just something that’s slowly getting back, coming off surgery. It started to feel a lot better, a lot more like what it used to.’’

Of the 75 strikes he threw, Sox hitters whiffed on 27 percent of them.

“He had pitches he could throw behind in the count,’’ Sox manager Bobby Valentine said. “His changeup was a real devastating pitch and his fastball was alive all night long. He’s special. He’s a very good pitcher, obviously.’’

Alex Prewitt can be reached at aprewitt@globe.com. Follow him on Twitter @alex_prewitt.