Rockies closer Seth Halvorsen never even turned around to watch the ball fly. He just walked off the mound knowing he’d given up a game-winning homer.

And interim manager Warren Schaeffer knew he’d made a tactical mistake.

James Wood, the Nationals’ rising star, launched Halvorsen’s 1-0 splitter 428 feet to center field for a two-run, 11th-inning, walk-off homer Thursday afternoon at Nationals Park. Washington won, 4-3, snapping its 11-game losing streak and putting the breaks on Colorado’s four-game winning streak.

Wood hit a two-run homer earlier off starter Chase Dollander, but Schaeffer decided to let Halvorsen face Wood with two outs and first base open. Bad decision. Wood’s game-winning blast was his 20th homer this season.

Asked by Rockies.TV if he considered walking Wood and pitching to Luis Garcia Jr., Schaeffer answered, “One-hundred percent. Obviously, the result says I should have, but I trust Seth in that situation. But that’s on me.”

Schaeffer said the Rockies talked in meetings about not letting Wood beat them, yet Wood produced all of the Nationals’ runs.

“I think I can look at myself in the mirror — better — if we lose to Garcia, next up,” the manager added. “It’s not like I don’t trust Seth to get (Wood) out, because I do, but I probably should have put him on.”The Rockies went 4-3 on their road trip, so that’s a success story for a team that owns a 17-58 record. But they blew a chance for their first four-game series sweep since winning four vs. Arizona at Coors Field May 27-30, 2019.

Colorado, on pace to lose a modern era record 125 games, is tied with the 1907 St. Louis Cardinals for the second-worst 75-game start in major league history. The 1932 Red Sox started 16-59.

Colorado took a 3-2 lead in the top of the 11th on Michael Toglia’s RBI single to drive in Ryan McMahon, who started the inning at second base.

Toglia, called up Monday after an 11-game stint at Triple-A Albuquerque to hone his swing, hit .352 (6 for 17) with three home runs, six RBIs and only four strikeouts over the four-game series.

Washington struck first, taking a 2-0 lead in the fourth on Wood’s two-run homer off Dollander. Wood, by far the Nationals’ most dangerous hitter, ripped Dollander’s first-pitch changeup 403 feet to center field. Dollander has given up 14 homers in 12 starts, a big reason why the rookie right-hander has a 6.19 ERA. His 2.2 home runs per nine innings ranks as the second-highest in the majors (minimum 50 innings)

Overall, Dollander pitched a strong game, giving up two runs on six hits over six innings.

He struck out two and didn’t walk anyone. He threw 81 pitches, 54 for strikes.

“Chase stacked two good (starts) on top of each other, one in Atlanta and one here,” Schaeffer said. “He was efficient. He was very good and definitely could have gone out for the seventh, but it was a really, really hot day.”

The Rockies tied the game, 2-2, in the fifth on an RBI double by Jordan Beck off Nats right-hander Trevor Williams. Mickey Moniak immediately followed with a single to right field to score Beck.

But the Rockies, who left 10 men on base, wasted several opportunities to win the game.

Still, Scheaffer said he was pleased with the road trip.

“That was a good seven-game stretch for us on the road,” he said. “If you take road trips by themselves, we won that road trip, which is a very good thing, moving forward. The boys are playing hard, the boys are playing good, and they are paying attention to details.”

The Rockies open a three-game series against the Diamondbacks on Friday night at Coors Field.