Dodgers manager Dave Roberts said he was already in “playoff mode” Wednesday, as his club continued to jockey for position in the crowded National League standings.

Once October actually arrives, however, he can only hope their potential postseason foes will make life as easy on them as the Seattle Mariners did Wednesday night.

In an 8-4, sweep-clinching defeat of the Mariners at Dodger Stadium, the Dodgers got almost as much help from their opponents as they did themselves.

At the plate, the Mariners’ listless offense, which entered the night last in the majors in both batting average and strikeouts, continued to pose little discernible threat, allowing Dodgers starter Jack Flaherty to cruise through a 5⅔-inning, two-run (one earned) start.

In the field, the Mariners’ sloppy defense turned star pitcher Logan Gilbert into something of a piñata, giving the Dodgers extra chance after extra chance to take a whack at the All-Star right-hander.

The result: A stress-free victory that marked the Dodgers’ fourth straight win and 10th in their last 13 games.

Tougher tests certainly await on the horizon.

But this week, the Dodgers did exactly what they were supposed to against a reeling Mariners team — reaffirming their place atop the league and division standings in the process.

At 76-52, the Dodgers have a one-game lead over the Philadelphia Phillies for the best record in the NL (and MLB). Even more important: They’ve regained a pocket of breathing room in the NL West standings, using Wednesday’s win to move four games clear of the San Diego Padres and Arizona Diamondbacks in a tight division race. It’s their largest NL West lead in more than two weeks.

The tight state of the standings is partially why Roberts declared himself to be in playoff mode prior to first pitch, even with more than a month remaining in the regular season.

Given his club’s struggles earlier this summer, and the questions that continue to surround its short-handed pitching staff, the manager was wary not to take anything for granted.

“The most important thing,” he said, “is trying to win baseball games.”

On Wednesday, the Mariners (who have squandered a 10-game lead in the American League West by going 20-33 since June 19) helped make that objective look rather easy.

The Dodgers took their first lead in the third inning, after a two-out error from Seattle shortstop Leo Rivas — on a ground ball from light-hitting No. 9 hitter Kevin Kiermaier — flipped the batting order to Shohei Ohtani, who walked, and Mookie Betts, who knocked in two runs with a double.

In the fourth, Teoscar Hernández advanced from first base to second on a stolen base (his seventh of the season), then from second to third on a wild pitch, positioning him to score on a one-out sacrifice fly from Will Smith.

Then, the game all but ended in a five-run fifth.

Like Hernández, Ohtani triggered the rally by advancing from first to third on a stolen base (his 39th of the season, matching his home run total as he approaches the 40-40 club) and wild pitch. Freddie Freeman plated him with a double, then took third on another errant throw that got away from catcher Cal Raleigh.

With two out, Rivas had a chance to end the inning on a one-hopper from Hernández, but couldn’t make a backhanded play in the hole at shortstop, letting the ball trickle into the outfield for another run-scoring knock.

It all culminated three batters later, when Max Muncy cashed in on a bases-loaded opportunity with a three-run double into right.

Muncy, who had another double earlier in the night on a well-struck grounder that got past former Dodgers star Justin Turner at first base, is now four for 10 with two walks, four extra-base hits and six RBIs since returning from an oblique strain that sidelined him for three months.

The night’s only real drama came early on, when the dugouts briefly cleared amid a shouting match between Flaherty (who gave up two runs, one earned, while striking out five) and Randy Arozarena.

In the second inning, Arozarena pulled a potential line-drive home run just wide of the left-field foul pole. When Flaherty’s very next pitch — a 91-mph sinker — plunked Arozarena in the back, the Mariners slugger stayed put in the batter’s box, glaring down Flaherty before taking his time walking to first.

An inning later, after Arozarena flied out to retire the side, Flaherty appeared to turn toward Arozarena on his way off the mound and shout something in the hitter’s direction.

As Arozarena raised his hands — as if to motion, “What did I do?” — both dugouts quickly emptied.

No physical altercation unfolded, however, with both Flaherty and Arozarena walking off the field before tempers truly flared. A high pitch from Flaherty to Arozarena during their third and final meeting in the sixth inning didn’t trigger anything further, either.

By then, the game was already effectively over, dropping the Mariners further out of the postseason picture, while moving the Dodgers another step toward October.