Janet Jackson performs at Chase Center in San Francisco on Sept. 21, 2019. Photos: Gary Chancer.

SAN FRANCISCO — Rarely does a performer set such high expectations, dip low into serious mediocrity, then pull off such an epic, mid-career comeback the way Janet Jackson did Saturday night at Chase Center.

And that was just during one show.

Jackson’s appearance in San Francisco was billed as a celebration of the 30th anniversary of her game-changing record Rhythm Nation 1814, a month after ending her 15-show Las Vegas residency. It’s one of just two non-Vegas shows she’s playing in the U.S. this year.

Janet Jackson performs at Chase Center in San Francisco on Sept. 21, 2019.

At first it seemed like she was pacing herself, as one might do playing multiple nights a week during a residency. It looked like the 53-year-old was accepting her veteran status and doing just enough for a packed house of equally middle-aged fans to remember who she used to be.

The last relevant member of the Jackson musical dynasty, she idled through the first portion of the show at a perfunctory pace, scattering bits of former hits around in medley fashion. Fans got a bit of “If,” some pedestrian chunks of “What Have You Done for Me Lately?,” “Control,” “Nasty” and the “The Pleasure Principle.” It seemed like Jackson, clad in flannel shirts around her torso and waist, was just cruising by.

Dancers danced and backup singers sang, but something felt wrong. She was flying through abridged versions of some of her biggest hits, and the evening started looking like a disappointment. When a performer as dynamic as Jackson promises to celebrate a record that sold 12 million copies and helped change the direction of R&B, she creates big expectations. You don’t expect someone merely swaying around her much more agile backup dancers, singing along to backing tracks while looking disinterested.

That relentless, hard, funky precision of 1989 was missing in action. Jackson had no edge and the material deserved better. There was a bit of life to “That’s the Way Love Goes”—at least enough for a big crowd singalong—and she found her sweet spot in the always gorgeous “Again.” After abbreviating “Together Again,” Jackson took a break 40 minutes into her set, and the whole thing started feeling like watching someone punch a time clock.

Janet Jackson performs at Chase Center in San Francisco on Sept. 21, 2019.

Jackson must have taken a power nap during the break, because she came back like her bright rust-colored hair was really on fire.

Well … eventually. She warmed up. She giggled a little. She bounced up and down. There was more sway to her hips. She started teasing and grabbing at her male dancers. Then after her band played an extended jam, she came back on decked out in true Rhythm Nation industrial gear. She and her crew lined up in formation, flame pots ignited on stage, and they delivered proper versions of “State of the World,” “The Knowledge” and “Miss You Much.”

Janet Jackson performs at Chase Center in San Francisco on Sept. 21, 2019.

The show went from wheezing through a musical school zone to merging into a high-speed police chase. “Escapade” lightened the tone some, without losing an ounce of energy, before the flame pots again filled the air with fire during “Black Cat.” The only place to go from there was a powerful, committed “Rhythm Nation,” during which Jackson’s voice strained with effort. The song was an exclamation point on an evening that ended nothing like it started. That is a credit to a great artist who probably shouldn’t be underestimated, even after all these years.