SAN DIEGO — The second half of the Dodgers’ season officially began Friday.

Which, for a slumping star bat like Kyle Tucker in particular, meant the small-sample-size argument had officially been invalidated.

The good news for Tucker and the Dodgers is that the $240 million offseason signing was back in the lineup for Friday’s series opener against the Padres, with Tucker returning as expected after a bout of back spasms sidelined him in Minnesota earlier this week.

Still, the back was far from the biggest problem facing Tucker as Game 82 kicked off at Petco Park.

A quick glance at his stat line — featuring career lows in batting average (.234), slugging percentage (.374), OPS (.707) and even defensive runs saved (-3) — tells a far more important, and ugly, story about a player who is earning the second-highest yearly salary in MLB history at $60 million; behind only Shohei Ohtani’s heavily deferred $70 million mark.

This year, Tucker has looked nothing like the four-time All-Star and transformational all-around threat he was billed as being.

He is swinging, whiffing and striking out more than usual. And when he makes contact, he is not hitting for average (his current mark is 35 points below his career norm) or power (he has six home runs and is on pace for a career-low 12, after never having fallen short of 20 in a full season).

A series of recent swing tweaks haven’t worked. A renewed focus on approach hasn’t helped him work better counts.

That’s why, when Tucker left Monday’s game early and missed the next two days nursing his back injury, manager Dave Roberts also hoped the absence could serve as a “mental reset” for the 29-year-old outfielder.

Four days later, Tucker and the team are hopeful that’s been accomplished.

“There were some things that they were working on, as far as on the mechanics side, before the back went out,” Roberts said ahead of first pitch Friday. “They built on that the other day. So, yeah, I think we got the mental reset and also physically he’s in a good spot.”

Tucker said his back pain subsided enough by Wednesday to be able to fully rotate through his swing, allowing him to resume his search for the right feel with his mechanics.

“Hit a couple times to make sure it felt good and then also just trying to get my swing right,” he said. “Just trying to have good backspin, stay inside the ball, stay through it.”

He also said he was confident the back injury was behind him, allowing him to avoid an injured list stint and bat sixth in Friday’s series opener.

“The ending of the swing was the biggest hurdle to get through,” he said. “Just because once you get there in a full rotation, it would kinda tighten up. But felt good that last day.”

Asked if he felt like he needed a mental reset, Tucker only offered a “maybe.”

But, he added, “you gotta show up the next day, regardless of what happened in the past. So just ready to get back in the lineup today and have a good day.”

Indeed, as the second half of the season begins, no one needs to start stacking good days as much as Tucker does.

His lack of performance hasn’t hurt the Dodgers yet. But in their pursuit of a third straight World Series, they’ll eventually need him to recapture something closer to his old form.