Overachiever — the word definitely describes pop and rhythm-and-blues star Usher.

During his 20-year career, Usher has sold 50 million albums, released nine No. 1 pop hits and 18 Top 10 pop hits and won eight Grammy awards. His extracurricular activities include coaching for TV’s “The Voice” and acting. He recently filmed the role of boxing star Sugar Ray Leonard in the Roberto Duran biopic “Hands of Stone.”

Known in show business by his first name only, Usher Raymond released his debut album in 1994. He was 15. At 14, the Atlanta teen and gospel singer appeared on TV talent show “Star Search” and subsequently auditioned for LaFace Records principal L.A. Reid.

Usher stepped on a starry path when his self-titled album debut went gold and produced the hit “Think of You.”

“My Way,” the singer-dancer’s second album, didn’t appear until 1997, after Usher’s high school graduation. “My Way” featured multiple hits, topped the R&B chart and nearly topped the pop chart.

Now 36, Usher is in the midst of his “The UR Experience” tour, which comes to the Smoothie King Center Saturday.

The 27-city “UR Experience” opened Nov. 1 in Montreal. Usher’s opening acts include 22-year-old New Orleans rhythm-and-blues artist August Alsina.

“With the ‘UR Experience,’ ” the star said in a statement, “I want to give my fans an ever-changing live show full of surprises and special guests. I am really excited to be with my fans and give them an Usher experience like they’ve never seen or heard before.”

But after being an overachiever for so many years, Usher’s studio prowess recently reached an impasse. The “UR Experience” tour follows the withdrawal from release of his projected eighth studio album, also titled “UR.”

Usher told Billboard magazine, “the album isn’t scheduled anymore. I’ve basically taken it back. … At the end of the day, all of this is just about having fun. You get in the studio (and) go with how you feel.”

The Hollywood Reporter quoted the singer as saying the album “just ain’t ready,” and needs more time to develop. Guests who recorded for the project included Nicki Minaj, Pharrell Williams, Ed Sheeran, Drake, Diplo, Skrillex and Chris Brown.

Unfortunately for Usher, the “UR Experience” tour may not be going so well either. Billboard gave Usher’s Nov. 4 show in Detroit a mixed review, describing it as “a combination of celebration and contextualization.” The set list, Billboard added, included new songs “She Came To Give It To You” and “Good Kisser” and “messy” remixes of “My Way,” “OMG” and “Love In This Club.”

A Hollywood Reporter review of Usher’s Nov. 7 concert at Madison Square Garden also judged that performance inadequate. Despite being a spectacle, the New York show overall failed to do justice to the star’s history and potential. Even so, Usher’s routines were cited as “sharp, effortless and even playful at times.”

Contrasting the latter mixed reviews, The Cleveland Plain Dealer gave an enthusiastic account of Usher’s Quicken Loans Arena show. The reviewer compared the athletic Usher to Cleveland Cavaliers basketball star LeBron James.

“The guy has Michael Jackson’s celebrated spin moves down to a science,” the review reported. And Usher’s stutter-step moonwalk, also borrowed from Jackson, “is nothing short of stunning,” critic Chuck Yarborough continued. Side note: Usher is a part owner of the Cavaliers who calls Cleveland his second home.

A Los Angeles Times reviewer noted how little new material appeared in Usher’s sold-out Nov. 21 appearance at the Staples Center. Nonetheless, the reviewer concluded, “an Usher show has long been an exhilarating affair packed with high-octane choreography held together by sleek, masterful showmanship. Friday’s show was no different.”