The phrase "already left behind" is correct and usable in written English.
It can be used to describe something or someone that has been abandoned or is no longer present, often in a context of progress or change.
Example: "In the rush to modernize, many traditional practices have already left behind their relevance in today's society."
Alternatives: "previously abandoned" or "no longer relevant".
Already left behind, I wanted to call out, like Orpheus, "Come back!
This picture stomps through the large, potent footfalls already left behind by "South Park: Bigger, Longer & Uncut".
In Chicago's suburbs and towns in Indiana and Michigan, residents were assessing the costs of damage already left behind in scores of soggy homes, cars and businesses.
But some, like Ms. Warshaw, can only see the trail of broken promises and failed hopes he has already left behind.
She ran an antiques shop and then a successful hotel in Wales, much favoured by London showbiz types wanting a break from the pressured world that Miss Drew had already left behind her, lightly, gracefully and decisively.
From all over the globe, in bits and pieces, data are accumulating that suggest we may have already left behind the world of possibilities portrayed in the panel's report.
The government has confirmed its determination to pursue a hard Brexit, even though that risks making matters worse for people who already feel left behind in this economy.
Martín Demichelis, Saturday's replacement for the Belgian, had already been left behind by a scampering Arnautovic before he punished City with the opener.
Lamps had already been left behind by a former English roommate, known to some as Mary Poppins for her keen sense of magic.
Levels and experience points have made their way into everything from gamification to bingo, but much of their context has already been left behind by a digitally native generation.
The second observed innovation, leaf-sponge re-use, where individuals re-utilize a leaf-sponge already made and left behind by another chimpanzee, is probably also a modification of leaf-sponging.
