Damian Lillard claims officiating in the NBA this season has been "unacceptable", as he did not expect to be impacted by the league's foul rule change.

A new interpretation of the foul rule in 2021-22 has seen a "change in the officiating of overt, abrupt or abnormal non-basketball moves by offensive players with the ball in an effort to draw fouls", essentially meaning fewer trips to the foul line for certain players.

Portland Trail Blazers star Lillard had attempted 484 free throws last year, the fifth-most in the NBA.

But that figure has dropped from 7.2 per game all the way down to 3.2 following the officiating changes, a huge factor in Lillard's points output decreasing from an elite 28.8 to 19.3.

Only in his rookie season has the point guard scored fewer points per game, while he has never averaged fewer free throw attempts.

Given Lillard scored 23.1 per cent of the Blazers' points in 2020-21, with only Stephen Curry on the Golden State Warriors contributing a greater share (24.6 per cent), this dip has had a significant knock-on effect.

Portland are 5-6 this year and one of only three teams still winless on the road, with their latest loss coming on Tuesday at the Los Angeles Clippers.

The Blazers had snapped a seven-game losing streak against the Clippers in the teams' previous meeting but went down 117-109 at Staples Center, where Lillard was furious with the officials, restricted to only one free throw attempt.

He has visited the foul line just three times in the past three games and let rip during his post-game media duties.

"I feel like the way the game is being officiated is unacceptable," Lillard said.

"I don't want to go too deep into it so they make a big deal out of it, but the explanations, the s*** that's getting missed, I mean, come on...

"I'm not that type of player – I felt like coming in, the rule change wouldn't affect me, because I don't do the trick the referees, I don't do the trick plays. It's just unacceptable, man.

"Then the explanations and the remarks in return when you're telling them is just like... I don't really have anything else to say about it."

For all Lillard's complaints, his shooting performance has also been down this year, averaging 36.5 per cent from the field, 25.5 per cent from three-point range and 85.7 from the foul line; he was 45.1, 39.1 and 92.8 last season.

These numbers were not helped by a hopeless performance against the Indiana Pacers last week, when he was two-of-13 from the field for a mere four points in 38 minutes.

Only once previously in his career had Lillard scored so few points while playing more minutes (four in 40 versus the Orlando Magic in 2013).

But he had a year-high 27 against the Clippers and added: "I'm feeling better each game. I still feel like I'm not completely rolling, but I'm feeling better every game."