Leeds consolidated their top-four spot in the Super League with a 41-16 win over Hull KR but it came at a cost with the loss of centre Harry Newman with a broken leg.
The 20-year-old, who was named in England coach Shaun Wane's squad earlier this year, was injured attempting a tackle 30 minutes into the match at the Halliwell Jones Stadium.
The game was held up while Newman had treatment on the pitch before he was carried off on a stretcher and taken to hospital.
"He's definitely broken his leg, his tib and fib we think," said Leeds coach Richard Agar. "We feared he had broken his hip as well but they're saying it settled down in the ambulance.
"He's having x-rays and they will tell us what the next step is but it will be a three to six-month job.
"It's a huge blow for him and we'll do our utmost to keep his spirits high. Typical of Harry, as he was coming off, he gave the thumbs up to the stand. He's a great kid, we love him to bits."
The Rhinos ran in seven tries, two of them from winger Ash Handley, as they took their points total in three games against Hull KR in 2020 to 141, but Agar says it should have been more.
"We created 14 line breaks and scored seven tries," he said. "The boys are disappointed. We could have had a bigger gap at half-time, we squandered a number of chances, but we can't be too disappointed."
The highlight for Hull KR was the promising debut of 18-year-old full-back Will Tate, who was brought in by Smith as one of 11 changes to the team that lost 48-18 to the Rhinos in the Challenge Cup a week earlier.
Smith said: "There are some similarities to last week with the way we started. You look up at the scoreboard and it's a bit demoralising.
"We didn't throw in the towel no matter what, there is a good spirit, we've just got to learn some lessons about how to start games.
"There were too many missed tackles and we're not playing the ball quick enough. But we can fix that up."
Smith defended his decision to ring the changes and revealed he was forced to perform an about-turn by playing three-quarter Shaun Kenny-Dowall, who scored one of Rovers' three tries.
"A lot of these guys needed a chance," he said. "Some of them have been training a long time without having a crack.
"And there are some boys who have put in some big efforts in the last few weeks who needed a break.
"Shaun Kenny-Dowall was going to get a break but someone rang up this morning ill and I asked him to play.
"He put his hand up. He's a great pro and a great example to the young blokes. And I thought it was one of his best games since been with us.
"I thought Will Tate was good. It wasn't a perfect start but he's come out of it on the positive side. He showed some real maturity at different stages and some pieces of class at different stages as well.
"The disappointment was that his parents weren't allowed to be here to see his first game."