LOS ANGELES -- Prolific offenses like the Dodgers’ can paper over weak links most of the time, but not on Tuesday night, when even Cody Bellinger’s 20th home run couldn’t stop the Mets from exposing the bullpen in a 7-3 loss at Dodger Stadium.

Left-handed-hitting Michael Conforto slugged a tie-breaking grand slam in the top of the seventh inning off Dodgers lefty Scott Alexander, after the Mets loaded the bases without hitting a ball past the mound.

• Box score

By inning’s end, the Dodgers had used four relievers. By game’s end, five Dodgers relievers had allowed five runs on five walks, two doubles, a triple, the grand slam and committed a throwing error in three innings.

Back-to-back walks issued by Yimi Garcia and Dylan Floro to open the seventh inning were the focus of manager Dave Roberts.

“You have to start getting ahead,” said Roberts. “The numbers don’t lie. I believe in those guys. They’ve all had their moments. We’re still winning baseball games, but there are things we certainly have to work out. They have to go out there and get outs, they do.

“When guys get ahead, they have a tendency to get guys out. And when you work behind, you don’t. Teams are always having discussions about the ‘pen, because that’s always forefront in mind. I know, those guys know, we need to get better and we’re working on it every single day.”

The Dodgers have the best record in the National League at 36-19, but the bullpen has been charged with 11 of those losses, along with eight blown save opportunities (only two by closer Kenley Jansen).

The only reliever of the five that did not give up a run Tuesday night was Joe Kelly, but he also worked around two walks and a wild pitch. His 8.35 ERA, after signing a three-year, $25 million free-agent contract, is an indicator of the disruption of management’s offseason strategy for resolving the revolving door of setup men.

Before the game, Roberts alluded to Kelly’s recent three-day stint on the bereavement list and the possibility there are off-field concerns in play.

“It’s been a tough road for Joe to start the season,” Roberts said. “I don’t want to get too much in what’s going on personally for him, but I think there’s things in people’s lives that sometimes affect performance.

“He’ll never make excuses, but if you look on the surface, it’s just execution. Getting behind, making mistakes with the fastball, it doesn’t matter how hard you throw. Guys these days can time a bullet. With Joe, we’ve got to work on getting back ahead and execute pitches.”

The bullpen has been further weakened by the continued shoulder problems of Tony Cingrani, who has yet to pitch for the Dodgers this year, and struggles by Caleb Ferguson and JT Chargois, both now in the Minor Leagues. The Dodgers also received stretches of solid pitching last year from Josh Fields, who was released in Spring Training.

Ross Stripling has picked up relief innings, but he hasn’t been nearly as effective out of the bullpen (6.75 ERA) as he was starting (2.65). Julio Urias is now in the bullpen, but his usage has been limited because of health concerns, compounded by a recent arrest and week on administrative leave.

Tuesday night’s bullpen meltdown negated a quality start from Rich Hill, Bellinger’s historic homer and a memorable MLB debut for Will Smith, who singled in his first at-bat, doubled and threw out a runner trying to steal second base.

“You would never have guessed it was his first big league game,” Roberts said of Smith, who also was behind the plate during the fateful seventh inning.

Garcia took over for Hill and walked the only batter he faced, Adeiny Hechevarria, in an eight-pitch at-bat leading off the seventh. Garcia came into the dugout and threw his glove and cap. Floro came on and walked pinch-hitter Aaron Altherr in a seven-pitch at-bat. Amed Rosario tried to bunt them over, but Floro fielded the ball and bounced it off David Freese’s glove for a throwing error that loaded the bases.

Floro struck out J.D. Davis, but Roberts went with the lefty vs. lefty percentages, only for Alexander to serve up his second home run of the season on an 0-1 sinker up that Conforto took the other way.

“The last four out of five outings, something like that, the ball’s been up and he’s had trouble getting it down,” Roberts said of Alexander. “A sinkerballer, when you’re elevating the ball tends to flatten out and now you’re exposing yourself to potential slug and that’s what happened tonight.”