Bentley left the field on a spinal board and was taken straight to hospital following a collision with Jake Connor early in the game.
Smith has allayed fears that the forward sustained a serious neck injury.
"He's okay," said the Rhinos boss.
"He was in a bad way there for a bit but he regained consciousness and is awaiting a scan to check his head and neck.
"The signs at this stage are that he'll be okay. He was talking to the doctor prior to getting into the ambulance.
"Precautionary is what the medical staff are saying."
In a do-or-die contest for the play-off hopefuls, Huddersfield raced into a 16-0 lead and held their nerve following a fightback by Leeds to move level on points with their West Yorkshire rivals.
The Rhinos were left aggrieved by several contentious decisions that went against them, including a late Connor one-pointer that ended their hopes.
"There was a drop goal that didn't go through," said Smith.
"The kicker and his mates were all laughing that it didn't go through. They were getting ready for a 20-metre restart.
"Everybody has said it didn't go through, except the decision-makers. A couple of Huddersfield players said it missed by a couple of metres.
"In the end, we had opportunities but some days it's hard to overcome all of those things."
The Rhinos are four points adrift of the top six with four rounds remaining after a 13th defeat of the season.
Smith is not giving up hope of a late charge for the play-offs.
"Every loss this year has felt like a massive blow and every loss in my life ever will be a massive blow," he added.
"Mathematically we are still right in the picture. I'd imagine we'll need four wins from four.
"Usually 14 wins in 27 rounds gets you there but we just need to get one next week first."
Sunday's result improved Huddersfield's slim chances but Ian Watson is realistic about his side's prospects.
"You'd have to (win all four games)," he said. "But we're not focusing on four games down the line.
"We've been focusing on one week at a time for eight weeks now and it's served us well, although we fell off badly last week.
"This week we showed some real resilience and character."
The Giants suffered a disappointing home defeat at the hands of Salford Red Devils in their previous outing but lifted for the derby and got their rewards.
Watson felt Chris McQueen led from the front on an emotional afternoon for the experienced Australian.
"We spoke as a group this week about responding," said Watson, who revealed Olly Russell sustained a suspected broken hand.
"We had some extra motivation in terms of Crispy playing his 250th and his mate (former South Sydney Rabbitohs team-mate) Kyle (Turner) passed away last week so he wanted to dedicate this game to him.
"The boys' efforts showed that. It was one that he would have been proud of and Crispy can be proud of as well. I thought he was outstanding."