Palmer joined Derby on a half-season loan from Chelsea in the final hours of the January transfer window, having only recently returned to his parent club from Huddersfield.
The 21-year-old spent the last 18 months borrowed by Town, for whom he scored five goals and created four in 32 appearances.
He'd have had more, surely, had it not been for injuries, although he still played a key role in Huddersfield's promotion to the Premier League via the play-offs.
Second-placed Derby are currently well-placed to go one better than David Wagner's side, and those of a Terriers persuasion are backing Palmer to repeat last season's trick, in the east Midlands.
Here's what they've been saying to their former player after his Twitter post on Thursday...
Good luck Kasey,you gave us loads of great memories..Derby have got a player.— ron sturgeon (@ronsturgeon1) 1 February 2018
Good luck KP wrote you name in towns history, no town fan will forget what you helped us achieve, the goals and nutmegs you never know what the future holds but you'd be welcomed back here anyday....hope to see you promoted again #nutmegsfordays #htafc #KP45— Christian J woodhead (@cjwhtafc) 2 February 2018
Good luck kasey Palmer, great memories made with huddersfield, hope you make many more with whoever you play for. Derby you have just signed a great player— Caleb Denniss (@itsXxCIDxX) 1 February 2018
Good luck. Go smash it, you'll always get a warm back at @htafcdotcom Shame about the injuries, could've really been the difference for us this season.— Steve Broomhead (@stevebroomhead) 1 February 2018
Good luck Kasey. If you can recapture the form you had for Town last season then you can get Derby promoted single handed— Jon Ewart (@JonEwart1) 1 February 2018
Will Palmer help Derby County to automatic promotion this season?