SAN DIEGO -- Marcus Stroman’s decision to accept the Mets’ $18.9 million qualifying offer this offseason came as a modest surprise in baseball circles, particularly after the right-hander had talked so openly about wanting to explore free agency. Evolving market conditions eventually changed his tune, and for that, the Mets were glad. One less thing to worry about.

As promised, Stroman has indeed strengthened the rotation, providing stability to a group that has needed it. With Carlos Carrasco sidelined indefinitely and David Peterson struggling, Stroman has not only slid into the No. 2 slot behind Jacob deGrom in the rotation, but looked the part as well.

His sharp outing in the Mets’ 6-2 win over the Padres on Sunday allowed his team to salvage a four-game split at Petco Park, despite consecutive losses to open the series. Stroman struck out seven over 6 2/3 innings, lowered his ERA to 2.41 and even contributed an RBI double to provide some late insurance.

• Box score

“He set the tone,” manager Luis Rojas said.

This was not Stroman’s most dominant start. It featured four walks, more balls in the air than he customarily allows, and just one 1-2-3 inning. But it showcased Stroman’s ability to make key pitches when he needs to. Thanks in large part to his sinker-slider combination and elite ground-ball rate, Stroman reminded those at Petco Park why he is one of the league’s best at inducing double plays.

It’s an ability that came in handy in the fourth inning, when the Padres loaded the bases on two hits and a walk. Stroman greeted the next batter with a first-pitch slider, which Webster Rivas grounded to third. Sliding to grab the ball just behind the bag, Brandon Drury slapped his glove on third then threw across the diamond from his knee to complete an inning-ending 5-3 double play.

“That was huge. I thanked him about a million times throughout the game,” Stroman said. “It’s a huge momentum shift right there when I’m able to get out of that inning pretty much unscathed … that gave me a lot of momentum to kind of propel me into the next innings.”

Stroman continued to thrive during that portion of the game as well, despite his own throwing error leading to the Padres’ only run off him in the sixth. By that point, the Mets held a cushy lead thanks to Billy McKinney’s RBI single, Dominic Smith’s solo homer and Pete Alonso’s run-scoring hit -- all off Padres starter Chris Paddack. Stroman added his own RBI double in the top of the seventh, and catcher James McCann later added his fifth home run in the last two weeks to suck any remaining drama out of the afternoon.

“It just goes to show how good this team is,” Smith said. “No matter who we play, we expect to win.”

Statistically speaking, that has been more due to the Mets’ pitching staff than their offense, which has taken the brunt of injuries throughout the first third of the season. And the pitching staff has been successful because its highest-salaried members have thrived.

As long as Jacob deGrom is around, Stroman will never be the anchor of this group. Even Taijuan Walker has garnered more headlines for his early-season success, making Stroman’s ERA only the third lowest on the starting staff. But it’s also 12th lowest in the National League, which speaks to how well the Mets’ top three starters have pitched.

The Mets do still lack starting depth, with both Carrasco and Jordan Yamamoto on the 60-day injured list. But so long as Stroman continues pitching this well, the Mets won’t need to stress over the situation. He has been arguably the most consistent pitcher on staff, delivering six consecutive outings of six-plus, with two or fewer earned runs in five of them. Only once this season has Stroman failed to complete five innings. Only twice in 12 starts has he allowed more than three earned runs.

“We never get too consumed or care about anything that’s going on outside the clubhouse,” Stroman said. “Whatever anyone needs to do to put themselves to the highest level, we’re very open to that.”

That’s not just talk. In winning Sunday’s game, the Mets ensured that by the time they take the field again on Tuesday, they will have spent 31 consecutive days -- a full month -- in first place in the NL East.

Despite all their injuries, the Mets have found a way to stay consistent. And it has begun with starting pitching.

“This team is incredible,” Stroman said. “I know we’ll battle through any adversity. What we’ve been doing is truly remarkable with having such prominent guys on the [IL]. And to have these guys step in and dominate, it’s been amazing to see.”