Wildcats, who won the Wetherby Whaler Festive Challenge 14-6 at rain-swept Headingley, lost hooker Scott Moore after the opening set of the game.
He suffered an arm injury, after being sidelined by a similar problem towards the end of last season.
“The only thing I am disappointed about is Scott Moore did his other biceps,” Wakefield coach Brian Smith said.
“That put a load on the team as well, losing him early.
“At half-time he said to me ‘at least I did it now - and I will be back ready for the start of the season’.
“I think he is pushing it a bit there, but he sees the bright side of things sometimes at least.”
Rhinos’ Australian No 9 Beau Falloon was concussed twice and did not return after leaving the field for the second time just before the interval.
Coach Brian McDermott said: “He looked half-decent in spells, before he got knocked out twice.
“He is all right, he won’t have any long-term issues there.”
Of Rhinos’ performance, McDermott said: “We are in the middle of pre-season so we probably got out of it what we needed.”
Despite the worry surrounding Moore, Smith was “very pleased” with his team’s display, though he felt the game could have been abandoned at or soon after half-time, due to heavy rain and a wet pitch.
He said: “I don’t care who wasn’t playing for Leeds, they still had a lot of good players out there and we kept them to one try.
“It was a real confidence-boosting start for Wakefield, I think.”
Smith added: “We had a lot of smart players.
“I was very pleased with that football intelligence aspect.
“There seems to be a bit of a bond there with them already as a group.
“Fitness was an important issue for us, but because of the taxing circumstances it is pretty hard to draw a proper line on exactly where we are.”