Newman made a blistering break to set up Rhinos’ first try in the 38-6 win over Hull, but left the field after just 11 minutes and did not return.
Assistant-coaches Sean Long and Jamie Jones-Buchanan were in charge of the team in place of Richard Agar who was isolating following a positive lateral flow test last week.
Rhinos’ Betfred Super League campaign begins against Warrington Wolves in 12 days’ time and Long said: “Harry felt his hamstring tighten up a little bit.
“We didn’t want to risk him so we pulled him off straight away and we’ll send him for a scan [today].”
On a more positive note, Jack Walker again impressed in his second comeback match following the foot injury which kept him sidelined throughout 2021.
He was introduced off the bench in the second half and Long noted: “He looked really sharp.
“He has been working hard in pre-season, he brought the ball back well so it was pleasing for him.”
Rhinos’ starting full-back Richie Myler scored one try and set up two others.
“Competition for places is what we want,” Long added. “Last year we were scratching around trying to find a team - at one point I thought I was going to put my boots back on.
“It is good to have competition, whether it’s in the centre, full-back, front-row or nine.
“It keeps everyone on their toes and I think you get the best out of your players.
“I think they are all going out there and putting their best foot forward.
“They want to get selected for that Warrington game.”
Winger David Fusitu’a got through 50 minutes in his first appearance for Leeds - which Long said was 10 minutes more than had been planned.
“He carried the ball back pretty well,” Long said. “He showed some good touches and his fitness was there - he got through the game unscathed, which was fantastic.”
A big hit from Fusitu’a led to Hull substitute Davy Litten being carried off on a stretcher, but both Long and visiting boss Brett Hodgson stressed it was a fair tackle.
Leeds were without prop Matt Prior and Long revealed: “He trained early in the week and felt his groin, slightly.
“He was going to play, but we decided not to.
“He is old enough, wise enough and knows his own body - he will be ready for round one.”
Of Leeds’ performance, Long reflected: “I thought we were pretty good.
“Our defense was solid in the first half, considering the amount of ball we had.
“We only had two sets in the first 10 minutes and Hull threw a lot at us.
“I was really pleased we only conceded one try, with the amount of possession and territory we had.
“We tidied up a few things at half-time and came out firing in the second half and scored three tries on the spin. There is still a bit of work to be done and that’s going to happen in pre-season games, no matter who you play, but I was pleased with the performance.”
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