Mets pitcher Robert Gsellman listens to pitching coach Dan Warthen...

Mets pitcher Robert Gsellman listens to pitching coach Dan Warthen as he is joined by T.J. Rivera and catcher Rene Rivera against the Dodgers on June 20, 2017. Credit: AP / Jae C. Hong

LOS ANGELES — At a certain point Tuesday night, it became hard to know what to make of the booms that rose above Chavez Ravine. Was it merely the sound of the home runs that the Dodgers used to beat the Mets into submission? Or was it the sound of nails being pounded into a coffin? Perhaps it was both.

Only time can determine if this indeed proved to be the end of a season that began with such promise. But this much was certain. With every blast that landed over the fence in a 12-0 deconstruction of the Mets, the Dodgers reinforced the notion that these two clubs no longer belong on the same field.

Sure, both teams began the season as contenders in the National League. But in late June, only the Mets (31-39) are flirting with total irrelevance while the Dodgers set their sights for much grander things down the road.

“It’s frustrating,” Mets slugger Jay Bruce said. “We obviously come here every day to prepare and take a lot of pride in being ready to play. We’re just not getting the job done.”

Robert Gsellman’s Southern California homecoming turned into a roast and the Dodgers cracked a season-high five homers. Three came off the bat of Corey Seager, who only narrowly missed a fourth, though he still finished with six RBIs. Rookie Cody Bellinger added home run, giving him three in his last two games, and upping his total to 22 in his first 52 games in the major leagues.

Through it all, the Mets looked helpless to stop any of it, a reminder of how their vaunted starting pitching has disintegrated into their most glaring weakness.

“I’m getting my butt kicked out there,” said Gsellman, who has allowed 14 earned runs in his last two starts.

The Mets are 11 1⁄2 games out of a spot in the postseason, though judging by their recent play, that gap in reality might be larger. In dropping three of four games against the Nationals — and now losing two games against the Dodgers — the Mets have looked hopelessly outclassed.

It is an alarming reality check. Should the Mets find a way to turn around a miserable season — and that notion grows more ridiculous by the day — these are the kinds of teams they will encounter in October. They have shown few signs of rising to that challenge.

For the third time this season, the Mets dipped to their low-water mark of eight games under. 500. To avoid sinking even further, they need a strong start Wednesday from Tyler Pill, who has spent most of the season in the minors.

“It’s frustrating because we know what kind of talent we’ve got here, what kind of pitchers we’ve got here,” catcher Rene Rivera said. “We’ve shown that we can pitch in the big leagues. Right now, we’re in a bad stretch. Nothing’s going our way. But we’re in the big leagues. We have to rally. We have to go back there and we have to be better.”

On Monday, the Dodgers needed just two innings to build a 7-0 lead against Zack Wheeler. The Mets lost, but at least showed some fight while nearly digging out of that hole against Clayton Kershaw. None of that resistance was apparent Tuesday, when the Dodgers took a 4-0 lead against Gsellman, who remained in the game even after it was long established it wouldn’t be his night.

“When you’re down 4-0 before you get an out, that starts to take a little starch out of you,” Mets manager Terry Collins said.

Gsellman last pitched at Dodger Stadium in 2009, when he was a sophomore at nearby Westchester High School. He tossed a shutout. But Tuesday, he faced a Dodgers squad that looks destined for a postseason run, one that has won five in a row and 11 of their last 12. There was no contest. The righty was charged with seven earned runs in 4 1⁄3 innings.

As he showed when he bailed out the Mets in the second half last season, Gsellman relies on a two-seam fastball to do most of his damage. He can’t afford to live up in the zone. But in what has been a year of regression for the righthander, his misses have been high, and the consequences have been severe.

The Dodgers made sure of it in the first. After Logan Forsythe hammered a leadoff single, Seager blasted the first of his three home runs. Two batters later, Bellinger found the rightfield pavilion with a two-run homer, which came after third baseman T.J. Rivera’s errant throw to allow Justin Turner to reach on an error.

Gsellman was chased in the fifth inning, when the Dodgers added five more runs. He became the first Mets pitcher to allow four homers in a game since Logan Verrett last August. Still, after the game, Collins said Gsellman would make his next start.

It was a telling declaration for the Mets, who have simply run out of other options. Injuries have deprived them of their ace (Noah Syndergaard), closer (Jeurys Familia), captain (David Wright) and middle infield (Asdrubal Cabrera and Neil Walker). The toll has become clear.

“We need to play better,” Bruce said. “Or we’re not going to make the playoffs. That’s the bottom line.”