Aaron Maybin's career took a surprising turn for the better last night -- 'cause after the linebacker was 86'd from the Cincinnati Bengals on "Hard Knocks," demand for his artwork went through the roof ... TMZ has learned.

Maybin's demise from the team was chronicled on the HBO docu-series last night -- along with his passion for painting. Cameras rolled as he worked on two pieces ... and his stuff was actually pretty good.

In fact, after the show ... Maybin tells TMZ his online gallery had “one of, if not THE biggest nights” of sales he’s ever seen.

AM says he was bummed out that his release from the team was televised -- telling us, "I turned my phone off last night, I just didn’t want to talk to anyone.” But when he turned it back on, Aaron says he was bombarded with messages from people asking how to get their hands on his artwork.

Maybin says he's feeling much better about his future today -- saying, "Regardless of whatever happens football-wise, I'm probably gonna make more money in my art career."