The Dodgers spent $308 million last winter to compile a star-studded roster featuring four MVP award winners — Shohei Ohtani, Mookie Betts, Freddie Freeman and Clayton Kershaw — enough quality arms to fill not one but two major league rotations, and a deep bullpen teeming with power arms.

The financial investments — more than $1 billion in Ohtani and Japanese right-hander Yoshinobu Yamamoto alone — clearly paid off, as the Dodgers entered Friday with an 84-56 record, tied with the Philadelphia Phillies for the best mark in baseball.

But as the Dodgers head into the final three weeks of the regular season, a time when they’re usually making their final push toward a National League West title, fine-tuning their roster and lining up their starting pitchers for the playoffs, they will approach October with a rotation of Jack Flaherty and … just who, exactly?

“We’re gonna have enough pitching,” manager Dave Roberts said, when asked if the rotation would be good enough to make a deep October run. “The names might be a little bit different. I don’t think anyone knows who [will] and who won’t be a part of it.”

Gavin Stone threw the latest wrench into the potential playoff pitching plans when the 25-year-old right-hander, the only member of the opening-day rotation who had not missed a start, was placed on the 15-day injured list Friday because of shoulder inflammation.

Stone, who is 11-5 with a 3.53 earned-run average in a team-leading 25 starts, is the 11th starter to go on the IL and joins a group that currently includes ace Tyler Glasnow (elbow tendinitis), Yamamoto (rotator-cuff strain) and Kershaw (left big toe inflammation).

Yamamoto, who has not pitched since June 15, is scheduled to return for Tuesday night’s game against the Chicago Cubs, but he threw only two innings and 53 pitches in his rehab start for triple-A Oklahoma City last Tuesday and will need several starts to build up his endurance.

Glasnow, who is 9-6 with a 3.49 ERA in 22 starts, was scheduled to throw off a mound Saturday for the first time since he went on the IL on Aug. 16, but Roberts acknowledged that “time is running out” for the right-hander to position himself for a potential October role.

“He’s getting off the mound and he’ll probably have a more aggressive bullpen session [this week], but we just gotta know, we gotta get going,” Roberts said. “We only have so much time before he [can] get built up and he’s pitching in major league games. Time is certainly of the essence.”

Kershaw, who returned from shoulder surgery in late June and went 2-2 with a 4.50 ERA in seven starts before injuring the toe on his push-off foot, is playing catch to keep his arm active but hasn’t been able to throw off a mound.

“He’s still trying to figure out the best way to provide relief [for his toe], and figuring that out is challenging,” said Andrew Friedman, the team’s president of baseball operations. “There’s not a playbook for that … it’s just not a common [injury].”

Stone will not pick up a baseball for at least 10 days, after which he will resume throwing, but when asked if he was optimistic about Stone returning this season, Friedman said, “I’m not sure … there’s just so much unknown, it’s hard to speculate right now.”

Friedman added that Stone’s injury is “really more symptom-based. It wasn’t something that was like, ‘Oh, we need to have surgery.’ It was, ‘Hey, let’s let everything calm down, pick up a ball and see where you’re at.’ If he comes back and feels good, I think we’re in a good spot. If he picks up a ball and has problems, then we’re in a tough spot.”

So, where does that leave the Dodgers? They’ll enter the homestretch with a rotation of Flaherty, Yamamoto, Walker Buehler (who showed promise in his last two starts after struggling in his initial return from elbow surgery and a hip injury), Bobby Miller (2-4 with a 7.79 ERA in 11 starts) and rookies Landon Knack and Justin Wrobleski.

“It’s been a really challenging year, certainly,” Roberts said of the pitching injuries. “I think other teams are going through it, and fortunately we have a lot of depth, we’re giving a lot of guys opportunities, and our guys have done a great job of not fretting, continuing to move forward and remaining positive.

“I think the main thing is whatever day we play baseball, you look at the locker room and see who is available, and you try to win a game that day. I don’t mean to sound insensitive, but that’s just the way we have to look at it.”

A thin rotation could put even more strain on a bullpen that recovered from a rocky July in which it posted a 5.65 ERA and had a major league-leading nine blown saves to compile a 3.55 ERA and a major league-high 12 saves and 28 holds since Aug. 1. And a prolific offense likely will have to out-slug some of the rotation shortcomings.

“Looking at our team big picture, I think this is arguably the deepest, most balanced lineup we’ve ever had,” Friedman said. “I think our bullpen is as deep and talented as I can remember. Now, we’ve got to figure out how to line up our starters, and as guys are coming back, making sure they get enough work under their belt to hit October in stride.

“We’re going to do everything we can to put ourselves in the best position going forward. All of our focus right now is on doing what we can to finish the regular season strong and be in the best position to go out and win, hopefully, 11 games in October.”