DON'T BLAME JASON DAY for not protecting his wife from that crazy collision with LeBron James at the Cavs game ... so says Jason's mother-in-law who says they're all just glad Ellie's okay.
Ellie Day suffered a concussion and was carried out of the arena on a stretcher after James accidentally ran into her at the game ... while she and her pro golf star hubby were courtside.
Some critics have gone after Jason -- saying he should have done SOMETHING to shield her from the blow ... but Ellie's mom says it's wrong to point the finger at Jason.
"I don't blame [Jason] at all," Lucy Knapp tells TMZ Sports.
"I love Jason very much. He's a wonderful father and husband. He also a great son-in-law. He cares about his family very much."
"I just thank God that she's okay."
Lucy says she cried when she saw the incident on television and refuses to watch the replays -- but says Ellie appears to be doing well and is now resting and recovering at home.