Off the field, Thursday was a nightmare for the Dodgers amid the Ippei Mizuhara/Shohei Ohtani gambling saga.

On the field, in the finale of their South Korean series against the San Diego Padres, things didn’t go much better for the team, either.

Star Japanese pitcher Yoshinobu Yamamoto flopped in his MLB debut, ringing in his record $325-million contract with a five-run outing that lasted just one inning.

An explosive offensive performance — keyed by a six-RBI outburst from Mookie Betts and four-hit performance from Will Smith — was wasted, with the Dodgers losing 15-11 after failing to erase an early seven-run deficit.

And, after an offseason of high-priced excitement and World Series aspirations, the team’s season-opening trip to Seoul ended up skidding somewhat off the rails, ending on an awkward note complete with scandal and sloppy play.

“This team has been through a lot, as far as the core guys over the years,” manager Dave Roberts said, downplaying the impact of Ohtani’s off-the-field drama compared to his team’s three errors (including two by third baseman Max Muncy), six walks allowed and 17 hits against.

“You’re just not gonna prevent runs that way,” Roberts said. “We just kind of got behind the eight-ball tonight.”

For that, they have their other big offseason acquisition largely to blame.

While all the pregame attention surrounded Ohtani and Mizuhara, the alarm bells quickly shifted to Yamamoto as he struggled to settle into his first career MLB game.

Coming off an underwhelming spring in which he suffered an 8.38 ERA and .357 batting average against, questions were quietly circulating about the challenges Yamamoto faced transitioning to MLB.

Compared to Japan’s Nippon Professional Baseball league — where the 25-year-old right-hander was a three-time MVP — the major leagues feature a different ball, a more rigorous schedule for starting pitchers, and hitting talent unmatched anywhere else in the world.

Still, after signing the largest guaranteed contract in MLB history this winter, neither Yamamoto nor the Dodgers could have imagined such a troubling opening act.

Yamamoto’s first pitch, a center-cut 96.6 mph fastball, was smoked by Xander Bogaerts for a leadoff single. His next batter, Fernando Tatis Jr., was struck by a wild splitter.

With still no outs recorded, Jake Cronenworth smacked a two-run triple to the right-field corner, prompting an early mound visit from pitching coach Mark Prior.

From there, Yamamoto appeared to lose his command — and his confidence — in a 43-pitch frame that slowly spiraled out of control.

Ha-Seong Kim hit a sacrifice fly to drive in a third run. Luis Campusano and Tyler Wade made it 5-0 after an RBI double and single, respectively. And by the time Yamamoto struck out Jackson Merrill to finally retire the side, Roberts had decided to turn to his bullpen.

“I wasn’t able to execute a pitch from the stretch,” Yamamoto said through his interpreter, Yoshihiro Sonoda. “I feel regret that I just couldn’t keep the team in the game from the get-go. So I do feel a responsibility for it.”

In Roberts’ postgame news conference, the manager tried not to overreact to his new pitcher’s growing list of early-season issues — which have included inconsistent command (Yamamoto threw 20 balls to just 23 strikes) and pitch-tipping tendencies that have already triggered a slight change in his delivery.

“He just didn’t have the command,” Roberts said. “It’s not about the stuff. When you’re a command guy — which he’s been his entire career, his life — and you misfire and get behind in counts and hit batters, that’s just not who he is. So we just gotta get back to refining the delivery, tightening up the command.”

Roberts was unsure how much the nerves of making his MLB debut influenced Yamamoto’s command.

But, Roberts insisted, “You know he’ll bounce back from this … I know he’s not running from it.”

Time will tell if such optimism comes to fruition.

Despite the early 5-0 hole, which grew to 9-2 after a four-run Padres rally in the third inning, the Dodgers made several attempts to claw their way back.

Betts punctuated a four-spot in the bottom half of the third with a double off the wall in left, then added a two-run home run with a fifth-inning blast to left.

A booted grounder by Bogaerts that was ruled a hit in the eighth plated a couple more runs, trimming the Padres’ lead to 12-11.

And before Manny Machado iced the game with a three-run homer off the scoreboard in the ninth, Ohtani made his last trip to the plate with the potential tying run in scoring position.

On the first pitch of that at-bat, however, the slugger rolled over a center-cut sinker from Padres closer Robert Suarez.

On their final day in South Korea, the stormy clouds above the Dodgers seemed impossible to lift.