Lance Stephenson is clearly emotional about his old pal Sebastian Telfair getting sentenced to 3.5 years in prison ... telling TMZ Sports, "That's like family right there."
Telfair -- a 1st round pick in the 2004 NBA Draft -- was found guilty of felony weapons possession stemming from a crazy 2017 arrest where cops say they found an arsenal of weapons, ammo, bulletproof vest and weed. He's currently serving out his sentence in a NY State Prison.
28-year-old Stephenson tells us he grew up playing ball and training with 34-year-old Telfair ... and still strongly believes his old friend is a good person who can get his life back on track.
"I know he's a good kid," Lance says ... "He's got great spirit. I know it's very tough on him and his family."
Lance added, "I'm trying to support as much as I can but it's very hard. That situation's very tough."
"I'm praying for him too. I think he'll be alright."
Telfair was facing up to 15 years behind bars, so he got off relatively easy -- but during the sentencing hearing, he begged the judge for even more leniency.
"Please don’t take me from the society right now," Telfair told the judge ... "I’m 34. I can go play in China for another six years, take care of my family."
The judge wasn't having it though and told the former high school phenom -- "The judgment in this case, sir, is what the jury convicted you of ... You’ve achieved greatness in your life, and this case doesn’t take that away."