Why The Avengers Don't Need An Infinity Stone To Turn Back Time
As already stated, the MCU is built on rules and restrictions, even to the most powerful of characters, and there's no way Captain Marvel will be exempt from that. If she was, there would be no villain powerful enough to have any real consequences. She would be a walking reset button and the MCU would suddenly have no stakes whatsoever.
So, it's likely that what Jackson is saying is not quite as straight-forward as it seems. But don't rule out the possibility that there's a grain of truth in there and that he's telling us that her powers will allow her to be the key to the other Avengers time travelling. That at least would make a lot more sense.
Perhaps the true power is actually related to an Infinity Stone, though?
Jackson also told Entertainment Tonight that the Tesseract would appear in Captain Marvel, which would represent the first time Nick Fury sees it (presumably explaining how it came into SHIELD's possession after Captain America's crash in the snow). Could the Tesseract be somehow linked to the Kree's powers? Could it be how Captain Marvel is so powerful in the first place? The same way Ronin as able to channel the power of the Power Stone in Guardians Of The Galaxy, despite it being suggested that anyone touching an Infinity Stone would die?
We know that the Tesseract's powers transport the wielder through space (hence it being called the Space Stone) and it might well be that the link between Captain Marvel and the Space Stone determines her ability to travel into the Quantum Realm. If the Tesseract is indeed the source of her powers - or partly the source - her being able to travel through space (and dimensions) would make a lot more sense and could explain what Sam Jackson was hinting at in terms of her ability to time travel.
That Stone might also be why the Skrulls are coming to Earth at all - as a means to defeat the Kree in their war. As if controlling the Tesseract would mean limiting or controlling the powers of the Kree's most valuable weapon: Captain Marvel. Or following the logic established in Infinity War and The Avengers that the only way to counteract powers created by an Infinity Stone is by using the same Stone (just as Scarlet Witch was able to destroy Vision).
The suggestion that she's powered in some way by the Space Stone isn't without some visual evidence either. If you look at the latest Captain Marvel teaser, there's a moment where she seems to go into a super-powered state and the colour of the energy emitting from her is very telling...
The Space Stone - and the Tesseract - are blue. Vision's powers and the Mind Stone are Yellow. Doctor Strange's powers and the Time Stone are green. When Jane Foster is infected by the Aether in Thor: The Dark World, everything turns red, which is the colour of the Reality Stone within the Aether. These colours are not accidental in any way. We're being given hints.
This is all speculation for now, but it might just all fit and it would explain the link between Captain Marvel, time travel, the Tesseract and the Skrulls.
Think you have a better interpretation? Share it in the comments thread below.