Firpo made his first start for Leeds in several months when he featured in their 1-1 draw against Rotherham United at the New York Stadium on Friday night.
The left-back recently came back to the mix following a lengthy injury layoff and is a popular member of the squad at Elland Road.
Newsome admitted that everyone around Leeds want him to succeed at the club, but stressed that he just does not have the defensive game to be a left-back at the West Yorkshire outfit.
The former Leeds defender insisted that Firpo lacks the basic traits that he would expect from a Whites left-back and that has continued to remain a major problem.
Newsome said on BBC Radio Leeds: “I think the biggest thing is that we do all want him to succeed and do well, but there are so many parts of his game that I question.
“Especially, the defensive side of it and I do scratch my head.
“I think he is a long way off.
“I thought his performance tonight was very mediocre at best and so yes, poor.
“I don’t think he has any awareness of what’s around him.
“He doesn’t recognise danger, he doesn’t know when to fill in, he doesn’t know when he can play short, when he can’t play short and when he can go long.
“He doesn’t want to stop a cross, doesn’t want to defend and all bits that I would expect to be the norm from a left-back playing at this football club.”
It remains to be seen whether Firpo can hold on to his place, especially with Sam Byram having impressed Daniel Farke.
