Lonzo's dad went on a tear against the Lakers coach on Tuesday saying Luke is to blame for Lonzo's uncertain future with the Lakers.

Remember, LaVar had previously said Lonzo was going to make an immediate impact in the NBA -- and he and LeBron would lead the Lakers to a championship, ASAP.

But now that Lonzo's on the trading block, LaVar is pissed and he's been bashing Luke Walton on the radio.

So, when we saw former Lakers star Derek Fisher -- who's now the head coach of the L.A. Sparks -- we asked if LaVar had a point.

"I'm not a member of the Ball family. Luke Walton is a friend," Fish said ... "What I do know is Luke is a great person and he's a great basketball coach."

There's a little buzz in L.A. that the Lakers could be looking for their next head coach -- but publicly, management is sticking behind Walton.

The awkward thing for LaVar Ball ... there's a real chance the Anthony Davis trade plans could fall through and Lonzo remains with the Lakers for the rest of the season.