Lamar Odom says he's "extremely disappointed" after being cut from the BIG3 basketball league -- saying he first learned about the move on social media ... and not from Ice Cube. 

"As most of you have heard, the @thebig3 decided to deactivate me for the remainder of the 2019 season," 39-year-old Odom said. 

"I respect @icecube & the other league executives, however, I am extremely disappointed with the way that this has been handled."

"Besides the embarrassment, it’s disappointing to read on IG that this decision had been made, especially without sharing it with myself or my manager."

In his statement, Odom acknowledges that he wasn't in prime shape for Game #1 -- but says he was told he'd have time to get stronger ... and was hoping to showcase his talents in Game #4 this weekend in Rhode Island, where he played his college ball. 

"The Rhode Island game that is happening tomorrow was the game I have been looking forward to the most as many people know that this is where it all started for me."

Despite his issues with being cut, Odom thanked Ice Cube and the BIG3, and said he's rooting hard for the league to grow. 

He also praised Cube for being "the only black male owning a sports league in the USA, just let that one sink in for a moment."

Odom concluded, "I hope that we can use this situation as a lesson to grow, heal and become better people. I salute all of you, thank you for the love & energy."

As we previously reported, Odom was cut earlier this week -- and league sources told us it was because he simply wasn't ready to play. 

Ice Cube spoke after the move and said he still loves Odom but the league needs players who are gonna play every week.