PHOENIX — Shohei Ohtani entered uncharted territory in his final pitching start of the regular season, shutting out the Arizona Diamondbacks over a season-high six innings in the Dodgers’ 5-4 walk-off loss Tuesday night.

The question now, with the start of the playoffs looming: When will the two-way star toe the rubber next?

After a season spent mostly in rehab mode as a pitcher, building his workload inning by inning as he slowly worked his way back from a second Tommy John surgery, Ohtani has checked every box in his recovery and looks primed for what will be his first career postseason pitching outing.

On Tuesday, his fastball was elite once again, topping out at 101.2 mph and accounting for five of his eight total strikeouts. The rest of his seven-pitch mix kept the wild-card-seeking Diamondbacks off balance, resulting in just five hits (all singles) and no walks.

Most of all, the right-hander was also efficient, needing only 91 throws to work past the fifth inning for the first time this year.

“Over the last three or four starts, there’s been a ramp-up of intensity and performance,” manager Dave Roberts said of Ohtani, who has given up one run in 19 ⅓ innings over his last four outings to finish the regular season with a 2.87 ERA in 15 starts.

“I think that was his plan.”

Now, it’s up to the team to make a plan for its postseason pitching rotation and figure out exactly where Ohtani fits within it.

Roberts has virtually guaranteed that the reigning National League MVP will be used as a starter in next week’s best-of-three wild card round (which the Dodgers are all but assured of playing in, even if they sew up an NL West division title that has a magic number of three.

And as things currently stand, Ohtani would be lined up to go in Game 1, after the team moved his weekly pitching schedule this month to have him start on Tuesdays. Coincidentally or not, Game 1 of the wild-card round would be next Tuesday.

The reasons for opening that series with Ohtani on the mound are obvious — from his electric stuff, to his penchant for performing in big moments, to ensuring he does pitch in a series that could end in only two games.

However, Roberts insisted team officials “don’t know yet” how their postseason rotation will be ordered. Between the ever-present concerns about managing Ohtani’s two-way workload, and the team’s other wealth of starting options in what has been a resurgent rotation over the last month, there’s debate to be had about how to best maximize their $700-million superstar.

The Dodgers could, for instance, opt to start the wild-card series with Blake Snell and Yoshinobu Yamamoto in Games 1 and 2, and save Ohtani for a potential Game 3. The benefit there: Ohtani could focus solely on his duties as designated hitter the first two games, and wouldn’t be required to play the day immediately after a pitching start (he is hitting only .138 in such games this season, and the Dodgers have made an effort to get him starts immediately before off days in recent months).

Because Ohtani isn’t as built-up as the team’s other starters, delaying his start could also ease the burden early in the series on a shaky bullpen, which coughed up a 4-0 lead Tuesday after rookies Jack Dreyer and Edgardo Henriquez combined to surrender three runs in the seventh, and closer Tanner Scott blew his 10th save in a two-run ninth punctuated by Geraldo Perdomo’s walk-off single.

“I think it just kind of gives us some options,” Roberts said of having Ohtani potentially lined up for a Game 1 start. “But the likelihood of him starting a playoff game in that first series is very high.”

Whenever Ohtani takes the mound again, the Dodgers are hopeful that concerns about his pitching stamina will be somewhat assuaged.

Up until this week, the team had a hard cap of five innings for whenever Ohtani took the mound. For the sake of his health, they were reluctant to waver from it, even when Ohtani had a no-hitter through five his last time out against the Philadelphia Phillies.

Prior to Tuesday’s series-opener at Chase Field, however, Roberts said that “if all goes well,” Ohtani would pitch into the sixth inning and that his leash could be further loosened in October after recent conversations between the player and club.

“I feel really good with the conversation I had with Shohei about how today could potentially play out,” Roberts said pregame. “This is me talking to the training staff, talking to Shohei, feeling like we’ve got a really good base now.”

Once the sixth arrived Tuesday night, Ohtani made Roberts’ decision easy. He had yielded just three hits to that point (one of them, a comebacker that got him in the palm of his glove in the third). The Dodgers had a comfortable early lead, after Teoscar Hernández homered in the second and belted a two-run, two-out triple in the top of the sixth (catcher Ben Rortvedt added a run with his first Dodgers homer in the seventh).

Five batters later, Ohtani’s night was done, the right-hander stranding a pair of sixth-inning singles by getting Gabriel Moreno to line out to center and retire the side.

The next time he takes the mound, it will be his first time pitching in a postseason setting. Whether it comes in Game 1, or later in the best-of-three wild card series, will now be up for the team to decide.

Bullpen reinforcements

The Dodgers have at least one bullpen reinforcement coming in this series, with rookie right-hander Roki Sasaki set to be activated on Wednesday in his long-awaited return from a shoulder injury.

However, the status of trade deadline acquisition Brock Stewart remains in question. Though Stewart completed a recent minor-league rehab stint, and was with the team in Arizona on Tuesday, Roberts said the club is still “making sure he feels good” after missing the last six weeks with a shoulder injury. It is unclear if he will be activated this week, as originally expected.

“[We’re] making sure he’s put in a position to feel good if he is activated,” Roberts said. “That’s no guarantee … We’ll know more tomorrow.”

Before Tuesday’s game, Stewart threw an extended flat-ground session in front of a team trainer and general manager Brandon Gomes. The three talked for several minutes once Stewart’s session was complete.