Sources with direct knowledge tell TMZ ... T-Swift is NOT going to be performing in any capacity during SB LVIII -- and that includes during the Halftime Show ... when Usher is scheduled to rock the house as a solo act.

Not only is Taylor not going to pick up a microphone to croon a tune ... but we're hearing there's no chance T-Swift will go anywhere near the stage, let alone step onto it.

In other words, our sources say there are zero plans to have her participate in the Super Bowl whatsoever -- outside of her just being there as a fan -- and Usher is going to have the spotlight all to himself in terms of live entertainment that day.

The reason this even has to be stated, explicitly, in the first place is because ... well, with Tay Tay cashing her ticket to the big game -- along with the Kansas City Chiefs -- her fans were rife with speculation that there might be some type of big musical surprise in store.

Makes sense, frankly ... she's the biggest pop star in the world right now, and her mere presence at the Super Bowl itself is enough to get the rumor mill whipped up, we suppose.

Of course, Taylor doesn't owe any favors to the NFL ... so even though her fan base might've assumed something was in the works, it's a little naïve -- everyone knows Taylor's a businesswoman, and she ain't working for free. More importantly though ... this is Usher's moment.

The other thing to consider is the fact that Taylor will have just arrived from Tokyo when she hits Vegas ... from none other than the last of 4 straight shows back-to-back-to-back-to-back.

So, yes ... Taylor will probably be pretty tired, and all her energy (we imagine) is going to be put toward her cheering on her man. It's gonna be an emotional rollercoaster ... and Taylor won't have the time or the will to put on a show. Plus, again ... her talents ain't free!

If you wanna catch Taylor in concert again in America, you'll have to wait 'til Fall. She won't be doing any "Eras" shows until at least October in the States ... Super Bowl be damned!