Chris Thile has been wowing audiences since age 8, but Saturday’s show at the Fitzgerald Theatre promises to be the biggest challenge in his 27-year career, with the public-radio world tuned in to hear if his ability to dazzle goes beyond the mandolin.

When Garrison Keillor announced last year that he was bowing out as host of “A Prairie Home Companion,” many wondered if a California-raised musician without tested storytelling skills was the smartest replacement. They’re about to find out.

The sold-out season opener kicks off Thile’s high-profile introduction as permanent host, with rock guitar star Jack White and alt-pop charmers Lake Street Dive.

“It’s exciting to see an old show get a fresh start and I hope Chris enjoys it as much as I did, years ago,” Keillor said Friday. “I had the advantage of anonymity, the show slipping in with no advance notice, no audience, no expectations, and he comes into a packed room, vast multitudes tuned in at home. ... [But] he knows what to do.”

It’s a pivotal moment for one of the nation’s most popular radio shows and its St. Paul-based distributor, American Public Media (APM), which owns Minnesota Public Radio. Of 692 stations that carried the program last season, 106 have opted not to renew it.

The show, which premiered 42 years ago, will retain a mix of music and comedy, as well as its core group of sketch actors. The Ketchup Advisory Board remains a fake sponsor. Sarah Jarosz and Aoife O’Donovan, two of Keillor’s favorite duet partners, will be in heavy rotation.

But there are decided changes, ones that may be startling for those used to homespun anthems and tales of pumpkin-carving contests.

For starters, there’s the guest list. Upcoming shows will feature soul-rockers Nathaniel Rateliff & the Night Sweats, Americana darling Jason Isbell and Prince favorite Esperanza Spalding — younger stars that were strangers to Keillor’s Lake Wobegon.

Pianist Rich Dworsky, the only holdover from the Guy’s All-Star Shoe Band, will be joined by members of Thile’s Punch Brothers, a group dedicated to making bluegrass hip to a new generation. The Keillor monologue will be replaced by guest comedians, starting with Irish native Maeve Higgins. Thile will focus his creative juices on an original song every week.

Audience members aren’t the only ones having to adjust. Voice actor Tim Russell, who joined “PHC” in 1994, was accustomed to getting a rough draft of Keillor’s script the night before the show with major rewrites only hours until air time. As of this week, he has already seen drafts for the next few programs.

“It’s different,” said Russell, who will return Saturday as the voice of Donald Trump and many other characters. “The dollar bill for ‘Prairie Home’ used to read ‘In Garrison We Trust,’ with him churning out scripts in record time. This week we had a table read. We wouldn’t normally do that.”

Winning over skeptics

Some are skeptical about the overhaul.

“To me the word ‘Prairie’ is important, and I’m not sure what in this new format evokes ‘Prairie,’ ” said David Thiel, content director for Illinois Public Media, which decided to drop the program for its listeners in central Illinois.

To win over naysayers, Thile worked the room last month at the Public Radio Program Directors Association conference in Phoenix, starting with a concert at which he jokingly announced that the brown-nosing had begun.

The Illinois broadcaster wasn’t impressed. “I’m not a music critic, but to me it was just loud,” Thiel said. “In all fairness, most everybody I talked to seemed to enjoy it. There are plenty of program directors who seem enthusiastic about Thile.”

Count KCUR’s Bill Anderson among them. The Kansas City program director, who will continue to carry the show, said Thile was generous, witty and likable in Phoenix, qualities that were on display last season when Thile was a frequent guest and occasional fill-in host. One week, he recruited Paul Simon, one of the biggest acts in the show’s history.

“I hope he succeeds for selfish reasons as I want my station and our industry to thrive,” said Anderson. “I also hope he succeeds because I like the guy.”

Dave Kansas, chief operating officer for APM, said Thile’s performance was so well-received that, when the 35-year-old appeared on a panel the next day, the audience broke into spontaneous applause.

“Program directors are tough critics, so to have them so excited was a pleasant surprise,” Kansas said.

Better than expected

APM, which was built on the success on “Prairie,” is feeling so good about the response that it has raised its initial expectations.

Executives thought the show would lose about a third of the 3.1 million listeners it had last season. Kansas now believes it may average as much as 2.5 million fans, an impressive number for a show that, in many ways, is starting over. It will continue to be broadcast in nearly all of the top 50 metro markets nationwide.

To entice stations, APM offered a slight discount in the fees it charges to carry the show — Anderson said his station will save $3,300, about 10 percent less than last season — but that includes just 13 new shows, and only five at the Fitz. The rest of the season will consist of Keillor reruns. By comparison, Keillor usually produced more than 30 shows a year.

The strategy is designed to retain Keillor fans while giving Thile more time to prepare for programs and recruit high-profile guests.

Friday at the Fitzgerald, Thile was deep into rehearsals, leading his young band through a lively cover of John Prine’s “Paradise” on a set that has ditched Keillor’s old porch but retained the lonely lamp post.

No one expects Thile to win over everyone in one night, or even one season — and that includes Keillor, who remains on board as executive producer.

“Sing your song, improvise, improvise,” said the old scout, offering some last-minute advice. “And remember that sometimes the mistakes turn out to be the high point.”