Bryan Fuller is stepping back from the showrunner role of CBS’ “Star Trek: Discovery” as he juggles production responsibilities on two other series, Variety has learned exclusively.

The decision was made late last week to hand the day-to-day showrunning reins to “Star Trek” exec producers Gretchen Berg and Aaron Harberts as “Discovery” gears up for the start of filming next month and a May 2017 premiere date. Fuller, who will remain an executive producer, will still be involved in breaking stories, and the show will continue to follow his vision for the universe that this latest “Trek” series will inhabit. Writer-director Akiva Goldsman is also expected to join “Discovery” in a top creative role. He’s envisioned as serving as producing support for Berg and Harberts, Fuller and exec producer Alex Kurtzman as they juggle the demands of the series that CBS is counting on to be the marquee selling point for subscriptions to its CBS All Access SVOD service.

Sources said there had been some strain between “Star Trek” producer CBS Television Studios and Fuller over the progress of production on the show, as Fuller is also juggling the final weeks of shooting and post-production duties on Starz’s upcoming drama “American Gods” and prepping a reboot of “Amazing Stories” for NBC. Fuller has penned the first two scripts for “Discovery” and has hammered out the broader story arc and mythology for the new “Trek” realm. But it became clear that he couldn’t devote the amount of time needed for “Discovery” to make its premiere date and with production scheduled to start in Toronto next month. In September, CBS pushed the “Discovery” premiere back from January to May in order to give the team more time to work out stories and ensure sufficient time for production of visual effects.

Berg and Harberts are close with Fuller, having worked with him previously on ABC’s “Pushing Daisies.” Goldsman, a feature vet who was also a consulting producer on Fox’s “Fringe” with Kurtzman, is also close with Fuller. The new structure was worked out quickly over the weekend in an effort to allow Fuller to remain actively involved albeit not on the day-to-day production level as originally envisioned. There’s also some internal stress at the studio that the lead character, described by Fuller as a female lieutenant commander, has yet to be cast.

Riker spent 7 years of TNG unready for Captaincy, @GretchenJBerg @AaronHarberts are ready. Thrilled to see them in command of the Bridge. — Bryan Fuller (@BryanFuller) October 27, 2016

Sources emphasized that CBS execs have been happy with the material that Fuller has developed to date but became increasingly concerned that he had too much on his plate and there was no willingness to delay the premiere date once more. Given that “Star Trek” is one of the Eye’s crown-jewel franchises, there’s no question that CBS has a lot at stake with “Discovery.” The show’s budget is said to be approaching the $6-7 million per episode range.

“We are extremely happy with the creative direction of ‘Star Trek: Discovery’ and the strong foundation that Bryan Fuller has helped us create for the series,” said CBS Television Studios in a statement. “Due to Bryan’s other projects, he is no longer able to oversee the day-to-day of ‘Star Trek,’ but he remains an executive producer, and will continue to map out the story arc for the entire season…Bryan is a brilliant creative talent and passionate ‘Star Trek’ fan , who has helped us chart an exciting course for the series. We are all committed to seeing this vision through and look forward to premiering ‘Star Trek: Discovery’ this coming May 2017.”

The news that Fuller would be the showrunner of “Discovery,” alongside Kurtzman, was met with a positive reception among fans of the series, given his background as a writer for “Star Trek: Voyager” and “Star Trek: Deep Space Nine.” Fuller enthusiastically led a panel at the summer’s TV critics press tour as well as Comic-Con, where he teased details about the series, including that there would be an LGBT character in the cast of the new show.

Fuller had also confirmed during the press tour session that the lead character of “Discovery” would be a woman. Although no casting has been announced, sources say most of the other roles on the show have been filled. The lead character has proven a far tougher assignment.