p]:text-cms-story-body-color-text clearfix”> Dodgers pitcher Roki Sasaki throws in the outfield before the Dodgers host the Minnesota Twins on July 22.

Dodgers pitcher Roki Sasaki throws in the outfield at Dodger Stadium before a game in July.

(Eric Thayer / Associated Press)

When rookie pitcher Roki Sasaki began a rehab assignment last month, in an attempt to return from a shoulder injury that cost him most of his debut MLB season, Roberts said the calculus would be simple for the Japanese phenom.

If he performed like one of the Dodgers’ best 13 pitchers, they’d find a spot for him on the big league roster. If not, they wouldn’t.

After four triple-A outings, the latter has become the somber reality for the 23-year-old right-hander. And now, his chances of rejoining the big league roster this season look all but dashed.

On Tuesday, Sasaki once again underwhelmed with the club’s Oklahoma City affiliate, giving up four runs (on a pair of first-inning two-run homers) in a five-inning, two-walk, two-strikeout performance. His fastball, which was advertised as a 100-mph weapon when he signed with the Dodgers this offseason, dipped back down to a 94.4-mph average. Overall, he now has a 7.07 ERA during his recent rehab stint. And on Wednesday, Roberts said there are no plans for Sasaki to rejoin the major league team for now.

“The performance, the stuff hasn’t been there,” Roberts said. “Against triple-A hitters, you would expect more.”

Sasaki, of course, still figures to be a key piece in the Dodgers’ long-term pitching plans.

Because he signed as an international free agent, the team was able to secure him for six seasons of control at the cost of only a $6.5-million signing bonus. In time, they remain hopeful he can realize his potential as a possible MLB ace.

This year, however, has become a lost cause.

In eight MLB starts at the beginning of the season, Sasaki suffered from a lack of velocity and wild command while posting a 4.72 ERA in 34 1/3 innings. The theory then was that his nagging shoulder injury was partially to blame. But lately, Sasaki has continued to struggle even after returning to what Roberts said was 100% health.

“Roki has gone through a lot this year, and he still has a ton of talent,” Roberts said. “We just want to see more.”

The Dodgers certainly don’t need Sasaki to make a World Series run. They currently have six starting pitching options on the big league roster, and a bullpen that is getting closer to full health thanks to this week’s activation of Michael Kopech and the expected returns of Alex Vesia (who will begin his own rehab assignment with Oklahoma City on Wednesday) and Brock Stewart later this month. Brusdar Graterol could also be a late-season option after missing all of this year recovering from shoulder surgery, but his outlook remains unclear.

“The bar is high right now, because we’re in a pennant race,” Roberts said.

Still, when Sasaki arrived as a much-hyped (albeit still-developing) prospect in the offseason, the idea was that he could immediately contribute in the big leagues.

Instead, his fastball is still lacking life, his performances remain inconsistent, and his plan for the rest of this season is up in the air. Roberts said the organization is set to “huddle together and figure out what’s best for Roki and how we can get the most out of him.”

“To warrant pitching on our staff right now, there’s got to be urgency on his part and really dominant performance,” Roberts added. “That’s the level of where we’re at.”