“This series is going to be a challenge,” Alex Cora said before the Red Sox and Washington Nationals opened their weekend series on Friday evening. “This is a group that, they’re gonna put pressure on us defensively, they’re gonna try to go from first to third, try to score from first.”

That, coupled with the home team’s ongoing struggles hitting with runners in scoring position – they entered the day with 267 men left on base, third-most in the American League – spelled trouble for Boston throughout the night, as they fell to the Nationals 5-1.

Tanner Houck’s eighth start of the season was no Maddux, but he rebounded from early scuffles to compile a strong seven innings. He held the Nationals to three earned runs on six hits, one walk, and one hit batsman. Despite only striking out four batters, tied for his second-lowest mark of the year, Houck gave his team chances, and finished his outing with back-to-back 1-2-3 innings.

Houck battled early on. After retiring his first five batters, the right-hander couldn’t get from out No. 2 to out No. 3 without allowing a baserunner in each of the next three innings. He gave up a single, double and two-RBI single to give the Nationals a 2-0 lead in the top of the second.

The visitors repeated their attack in near-identical fashion in the third, tacking on another run on a two-out double by Luis García Jr., who scored on former Red Sox minor leaguer Joey Menses’ single. Houck’s two-out walk to Trey Lipscomb amounted to nothing, as he got Victor Robles to fly out to end the top of the fourth.

“Just finding a hole,” Houck said of the hits in questions. “Try not to beat yourself up too much about it, but it definitely stings.”

“Kind of fought my delivery in the first five innings, made an adjustment after that and delivery synced up a lot better,” the righty said. “Legs were kind of just lagging behind in the delivery and just not really getting the lead leg out there. I was kind of just getting stuck and I felt like I was just drifting down the mound a little bit too much.”

“Everything pitch-wise was a little flat,” he added. “Slider was the best pitch today in terms of movement and everything like that. Wish I would’ve gone to it a little bit sooner.”

After hitting the leadoff man to begin the fifth, Houck retired his last nine batters. It was his fifth consecutive start of at least six innings, and he’s pitched at least 5.2 innings in each of his eight games.

“He went seven. They put the ball in play twice in (the second and third inning) and they got rewarded. But overall, he induced the weak contact,” Cora said of his starter. “He’s been great for us. What (the Nationals) do, they put the ball in play with two strikes. They don’t hit the ball hard, but they find ways to get hits, and for him to go seven and give us a chance to win, another good one for him.”

Brennan Bernardino pitched a 1-2-3 eighth, so the Red Sox were still trailing by two runs when the manager went to his closer. Kenley Jansen opened the ninth with back-to-back strikeouts. But with two outs, the Nationals struck again. Eddie Rosario promptly stole second, advanced to third on an error by catcher Connor Wong, and scored on a wild pitch. Jansen walked Lipscomb, who also scored on Robles’ single before Jansen ended the frame with another punch-out.

Ultimately, though, the death knell was the same as it’s been over this frustrating seven-game stretch, during which the Red Sox have scored no more than two runs six times. They’d out-hit the Nationals until Robles’ RBI single in the ninth, but unlike their guests, had only one run to show for it. All told, the Boston bats were 1-for-9 with runners in scoring position and left 11 men on base.

“We didn’t get the big hit,” Cora said. “At one point, we’re gonna get the big hit, and we’re gonna get in that groove, right? But it didn’t happen tonight.”

The Red Sox collected eight hits and drew five walks, but found creative ways to squander runners. They almost took the lead in the bottom of the first when Tyler O’Neill hit a ball off the Green Monster for a two-out double and Rafael Devers followed with a walk. But when Wong singled to right, Robles threw home, where Keibert Ruiz tagged O’Neill out on the third base line to end the inning.

Like this weekend’s opponent, the Red Sox know how to turn up the pressure when they get on base, and did so in the bottom of the fifth. Ceddanne Rafaela and Jarren Duran showed off their speed, beating throws to first for back-to-back singles. The follow through, however, continued to be lacking, as Rob Refsnyder, O’Neill and Devers went 1-2-3 to strand Rafaela and Duran.

In the bottom of the sixth, Boston loaded the bases against reliever Derek Law, only to have Duran strike out looking when the Nationals subbed in another southpaw, Robert Garcia. The frustrated Red Sox leadoff man had words with home-plate umpire Chris Conroy before walking back to the dugout to exchange his bat for his glove.

“With two outs, RBIs, that’s not easy,” Cora said. “It’s the one before, second and third, less than two outs. You have to cash in.”

Refsnyder led off the bottom of the seventh with a walk, only to be erased when O’Neill grounded into a double play. When Devers struck out to make it a 1-2-3 inning, he did so on a pitch that hit him.

By the time Wilyer Abreu led off the ninth with a double, the Red Sox had failed to score in 23 consecutive plate appearances with runners in scoring position. Rafaela and Duran struck out before Refsnyder drew a walk. O’Neill struck out to cement the loss.

“It’s just baseball, man. It’s just one of those stretches, we’re getting pitched to really good, and it’s just not happening, but I know we’re gonna come out of it,” Duran said. “We all know that there’s ups and downs and we gotta ride the waves.”

The Red Sox are back down to .500 for the first time since March 31, during their first series of the season in Seattle.