Whoa -- this is BAD news ...

Britney Spears' longtime manager Larry Rudolph is speaking out about his client and friend and the message isn't good ... he says Britney may never perform again!

Rudolph tells TMZ: "As the person who guides her career -- based on the information I and all of the professionals who work with her are being told on a need-to-know basis -- from what I have gathered it's clear to me she should not be going back to do this Vegas residency, not in the near future and possibly never again."

That's serious! Rudolph isn't involved in Brit's conservatorship so he doesn't really have too much say in what she does or doesn't do, professionally and certainly not personally, but he's probably still the one negotiating the business deals so if he says she can't perform, the likelihood he'll be involved in reviving her contract with Planet Hollywood for her residency at the Las Vegas resort ain't that great.

Rudolph says Britney's recent breakdown came at a crazy time ... "It was the perfect storm. We had to pull her show because her meds stopped working and she was distraught over her dad's illness."Last summer, when she wanted to tour, she called me every day. She was excited. She hasn't called me in months. Crickets. She clearly doesn't want to perform now." He says now, he doesn't really want her to work again: "I don't want her to work again 'till she's ready, physically, mentally and passionately. If that time never comes again it will never come again. I have no desire or ability to make her work again. I am only here for her when she wants to work. And, if she ever does want to work again, I'm here to tell her if it's a good idea or a bad idea."

Man; it's serious!