The threat of severe weather that never arrived delayed the start of Wednesday’s game at Nationals Park by 25 minutes. (Mitchell Layton/Getty Images)

Ian Desmond stood on third base, helmet in his right hand and hands on his hips. By the backstop to his left, two umpires listened to black headsets stretched over their ears. Players in the Washington Nationals dugout murmured to each other. They all waited to find out if Desmond had hit a home run and given the Nationals the lead, or if he would stay on third base. An action-filled game would be decided by 3 minutes 42 seconds of inertia.

“I was just wondering what I was going to do if they messed it up,” Desmond said.

They did not mess it up. Joe West, one of the umpires, pulled off his headset and twirled his right index finger. Desmond tugged his helmet on and jogged home. The blast that skipped off the top of the right-center field fence, off a white railing and back into the field had pushed the Nationals ahead in the seventh inning, the decisive run in their sweep-sealing, 4-3 victory over the Colorado Rockies.

In their fifth straight win, the Nationals erased an early three-run deficit behind Doug Fister, who never buckled as he labored through seven innings. Jayson Werth sparked the comeback — and continued his surge — with a two-run homer in the fourth inning.

Rafael Soriano stranded men on the corners in the ninth for his 20th save, pumping 94-mph fastballs as he lowered his ERA to 1.06. He punctuated the pop-up he induced from pinch hitter Josh Rutledge with two vicious yanks of his shirttail.

Jayson Werth gets a hand from Adam LaRoche and Anthony Rendon after Werth’s two-run home run in the fourth inning. (Alex Brandon/Associated Press)

“Watching on TV or watching from the stands, his misses, people take those as uncalculated,” Desmond said. “But he knows exactly what he’s doing, exactly where he wants to put the ball, and he executes a lot. . . . I’ve started to kind of learn what his sequences are. I’ve got 100 percent confidence every time he takes the mound.”

After the Nationals moved ahead, Manager Matt Williams removed third baseman Ryan Zimmerman in the eighth — his excellent, diving play earlier in the evening notwithstanding — to make a defensive upgrade. Anthony Rendon moved to third, and Danny Espinosa entered at second.

“At that point,” Williams said, “we want our finest defense in there.”

More customarily, he put Tyler Clippard on the mound. With two outs, Justin Morneau rolled a single into right field. “Darn it,” Clippard thought. Rather than a groundball out for a clean escape, he had to face Troy Tulowitzki, perhaps the best player in the National League, as the tying run.

Because of his own previous patterns, Clippard suspected Tulowitzki would sit on offspeed pitches. So Clippard fired fastballs. Tulowitzki fouled back one at his chin, then took a generous strike two on the outside corner. He fouled away another fastball.

Clippard believed he had Tulowitzki set up not for his trademark change-up, but his secret weapon. Clippard experimented with his splitter — “splitty,” he calls it — for years, playing catch in the outfield. He started using it in games late last season. As opposed to his change-up, it requires no touch, which is what he likes about it. He can simply throw it as hard as he can and hope he buries it. “It’s a mindless pitch,” Clippard said. “Grip it and rip it.”

Against Tulowitzki, Clippard unleashed a splitter from hell. Moving at 85 mph, the pitch hurtled to the plate until it nosedived into the dirt. Tulowitzki corkscrewed in the batter’s box as he swung and missed.

The Post Sports Live crew debates whether Bryce Harper's comments about manager Matt Williams's lineup are potentially damaging for a team that just got back to full strength on Monday. (Post Sports Live/The Washington Post)

Desmond’s 15th homer, a blast to right-center field, had put the Nationals in position to tab the back of their bullpen. Fister had allowed it to happen. His defense complied with several sterling plays, including Desmond running down a shallow flare in the first. He refused to change his style even as his sinker lacked bite and curveballs hung. Fister allowed seven hits and several more hard-hit outs, but he did not walk any Rockies, and he leaned on his defense to close with five scoreless innings.

“It was definitely not my best stuff,” Fister said. “It was definitely a battle all night. At that point, it becomes a really big emphasis on team baseball, and letting those guys work behind me. Saying, ‘Here it is,’ and let them hit it.”

At the start, nothing went right. The Nationals delayed first pitch because their forecast called for rain, but when none arrived they had only wasted 25 minutes.

The delay interrupted Fister’s routine, and he settled in late. Michael McKenry blasted a three-run homer in the second. In three innings, Fister allowed the homer and six fly outs to the outfield. That’s usually more than an entire start for him.

On offense, the Nationals clobbered balls at Rockies or fell victim to highlight defensive players, including a balletic double play by Tulowitzki and DJ LeMahieu. Despite Fister’s rough start and hard luck, the Nationals never doubted.

“I don’t think we ever think we’re out of it,” Williams said. “We think we have a chance at any time.”

Rendon drilled a single to center field to start the fourth and stole second. Up came Werth. On Tuesday night, Werth hammered a foul ball into the upper deck in left, and something suddenly felt right in his swing. He cracked two doubles and drew two walks Tuesday. In his second at-bat Wednesday, Werth launched Tyler Matzek’s 3-1, 93-mph fastball into the first row of red seats.

Werth’s seventh homer — his first since June 11 — ended a 78-plate appearance drought and pulled the Nationals to within a run. With two outs, Bryce Harper blooped a double into left field, naturally losing his helmet somewhere around the batter’s box. He scampered to third on a wild pitch.

Harper danced off third base, forcing Matzek to peek over his shoulder and third baseman Ryan Wheeler to account for him. With Wheeler playing a step closer to third, Desmond poked a single through the hole on the left side of the infield, past Wheeler’s dive. Harper trotted home to tie it at 3.

The Nationals would put the game away after Desmond’s rocket to right-center and an anxious wait. They had won for the ninth time in 12 games, they had a day off to look forward to and nothing could mess them up.

“We have everyone healthy,” Zimmerman said. “I think we’re just playing better baseball, better defense. Our pitching has been great all year and now we’re scoring runs for them. I think that’s a good combination.”