The exciting young centre has not played since suffering a double break to a leg against Hull KR in September but returns for the game against Catalans Dragons in Perpignan.
Newman is set to start and Agar conceded: “It will be good to get him back after a big, traumatic injury.
“He has had a couple of setbacks towards the end and maybe not got back to full training as quick as he would have liked.
“He has had to trust the healing process a bit more and be a bit patient with it, which has caused him some frustrations, but he is good to go.”
The coach has no issues throwing the 21-year-old – part of England’s elite training squad ahead of the World Cup – straight in against the Super League leaders.
Agar said: “He looks a picture physically. Of course, we would expect him to be lacking top-line match fitness.
“Contact-wise, he has done plenty of training, but you never quite get used to game conditions until you play a match or two and get back into it. But he is super-fit and ready to go.”
Young half-back Callum McLelland could also make his first appearance of the season after a succession of injuries slowed his progress.
He is out of contract at the end of the year and needs to earn a deal – either at Leeds or elsewhere.
Agar said: “He has certainly got the rugby league IQ and intelligence. As a young half it is not always that easy, coming into a team where you’re not familiar with combinations, which has happened to him in the past.
“He came in last year at a time when we did have some disruption in our line-up so he was put in some difficult circumstances. There is a dearth of young half-backs in the game and it will be good for Callum this year to be in good shape to take any opportunities and hopefully give us some tough decisions moving forward about where he stands in regards to our starting line-up.”