Co-hosts Matt Lauer (L) and Savannah Guthrie on the set of NBC's 'Today' show. (BRENDAN MCDERMID/REUTERS)

He replaces Jim Bell, who one day earlier was sent back to NBC Sports in the wake of the morning show’s ongoing ratings tumble and his botched Ann Curry-to-Savannah Guthrie co-host swap-out.

Nash will report to Alexandra Wallace, who has been handed this headache and the title Executive in Charge of “Today.”

Nash will be responsible for all four hours of “Today” program content, NBC said in Wednesday’s announcement.

“Don Nash deserves to be at the helm of ‘Today,’” NBC News President Steve Capus said in detailing the show’s latest shuffling.

“He is a beloved member of the ‘Today’ family who brings vision, commitment and a deep familiarity to all aspects of the broadcast. The formidable individual talents of Alex, Don and the ‘Today’ leadership are now combined, and I’m confident our team is well positioned for success.”

And here’s something you don’t often see: Wednesday’s announcement included a bit in which the guy who got pulled from the job slapped the new guy on the back.

“I am thrilled for Don and for ‘Today,’ ” Bell was quoted as saying.

“I know firsthand the show will benefit from Don’s unmatched morning-television experience, control-room skill and leadership.”

Well, if Bell knew all that, why didn’t he take advantage of it while the show was going down, under his watch?

This season, “Today” is logging its smallest audience in nearly two decades.

In April, ABC’s “Good Morning America” ended “Today’s” longtime weekly ratings winning streak. “Today” hasn’t scared up more viewers than “GMA” since returning from the London Olympics, despite the Curry-for-Guthrie swap-out.

Anyway, Nash is a whopping 23-year veteran of “Today” and, over the past seven years, has orchestrated the live broadcast from the control room each morning and played an integral role in day-to-day programming.

Nash began his career at NBC in 1989, as a page in Burbank, Calif. After completing the network’s Page Program, he became a production assistant at “Today’s” Burbank bureau. Over the next 10 years, Nash got promoted to associate producer and producer, and in 1999 moved to New York to become a senior producer for the show.

Maybe more to the point: In 2002, Nash was named executive producer of “Weekend Today,” where he ran all aspects of the show, including content, marketing, sales and finance — as the show garnered all-time ratings highs.

In 2005, he returned to the weekday edition of “Today” as senior broadcast producer.

Wallace, meanwhile, moves up a notch on our News Execs Deserving of Our Sympathy list; she’s going to continue as executive producer of NBC News’s troubled prime-time newsmag “Rock Center With Brian Williams” — a.k.a This Season’s Least-Watched Prime-time Program on a Big Four Network That’s Not Called “Kitchen Nightmares.”