Here's video of Antonio Brown working on deep balls with Washington QB Dwayne Haskins ... and we gotta say, the two certainly have chemistry that could carry over to FedExField!!!

The free-agent receiver hooked up with the 'Skins quarterback Wednesday for a workout in Florida ... and the two got in some impressive throw-and-catch work.

Check out the clips Brown posted from the training sesh ... there were some 50-yard dimes that had people going crazy over the completions!!

Of course, there were other pros in attendance -- Geno Smith and Stefon Diggs (plus Chad Ochocinco!) namely -- so we're not too sure how much to read into this being an indicator of future NFL plans.

Then again, Brown has been working his ass off to get back into the league ever since the Patriots cut him last September ... and the Redskins could certainly use the help.

AB claims to have walked the straight and narrow since a myriad of legal issues cropped up over the last year ... issuing apologies to the NFL, his family and even local law enforcement.

The NFL, though, is still investigating all of the allegations against Brown ... and a lengthy suspension could be on the horizon.

But, after that, could D.C. be the receiver's landing spot???