Rhinos ran in five tries in the first half, but Trinity dug in to outscore them 18-4 after the interval.
It was Rhinos’ first of the season, at the fourth attempt and Agar said: “I think we’ve been close in two games.
“We just needed to play with the ball a bit more and find some more energy.
“Our boys turned up with the right attitude and some inclusions back in the team helped.
“We set our stall out with some really good quality ball movement and the confidence we got off that was good.
“It was a step in the right direction and we’re obviously pleased to get off the mark.”
Agar insisted Rhinos did not ease off in the second half and pointed out they played the final 15 minutes with 12 men, after Kruise Leeming was sin-binned and Blake Austin went off for a head injury assessment.
Harry Newman came into Rhinos’ side after a pre-season hamstring strain, but hobbled off in the second half.
Agar said Austin was “fine” after his head injury assessment and added: “Harry felt his hamstring a bit, it was precautionary.”
Trinity coach Willie Poching was forced to field a makeshift backline and admitted: “The first 20 minutes had a big impact on the game.
“They played extremely well, they came with a plan and got to some areas of the field they tried to expose and it worked at times.
“The scoreboard got away from us, but I was really proud of the response in the second half.”
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