James Hook was set to play centre for Wales in North America this summer
Lions coach Ian McGeechan challenged James Hook to match the efforts of Stephen Jones and Ronan O'Gara at fly-half after handing him a starting spot.
"We want him to control the side from the start like Ronan and Stephen in the first two games," he said after naming his side to face Free State Cheetahs.
Osprey Hook, 23, was a late injury call to the tour after a poor season.
"There are big boots to fill with Ronan and Stephen, but I will try and make a selection headache there," said Hook.
"There is no point coming here and sitting back, I've got a great chance on Saturday to give it my best and I'm going to give it 100%."
Hook featured off the bench during Wednesday's 74-10 victory against the Golden Lions, scoring an interception try and kicking three late conversions.
"James got into the game very well on Wednesday when he went on," acknowledged McGeechan.
"He's a good attacking player. He's keen, and he is obviously a very important driver of what we want to do and how we want to do it."
On the hard grounds of South Africa, the fly-half now has a chance to push for a Lions Test place, facing Super 14 strugglers Cheetahs at Vodacom Park.
I have been moved around a little bit this season more than I would have wanted. I do see myself as an outside-half
It is a far cry from a proposed place at centre on Wales' summer tour to North America with coach Robin McBryde claiming he did not know Hook's best position.
"[Lions assistant coach] Rob Howley told me after the game on Wednesday that I would be starting on Saturday. I am thrilled to bits," said Hook.
"I have grown up with rugby since the age of six, and this is the best you can achieve. It means the world to me.
"Fly-half is my preferred position. If it means playing, I would play anywhere in the back-line, but I do prefer 10.
"You get the ball in your hands a lot more and it helps my game playing at 10, just trying to control people.
"I have been moved around a little bit this season more than I would have wanted.
"I do see myself as an outside-half but I am just happy to get that start.
"You play wherever you are picked, so if it means playing centre or whatever then I will do that.
James Hook will seek inspiration from Lions greats like Barry John
"It is such a team game, and the moment you start going off on your own, things start going wrong.
"It is a great structure here, so if we play well collectively, the individuals will too.
"It is a great honour just to be out here, and I want a good performance on Saturday."
If Hook requires extra inspiration, he will find it written in the Lions dressing room when he arrives at Vodacom Park.
He will go to his appointed changing peg - and then see some of the greatest fly-halves in Lions' history etched under his name.
"They put the names up on the board in the changing room before the game, which is pretty special," he said.
"It reminds you of how special the jersey is and what a great honour it is to wear it.
"The previous players who have worn the jersey you are wearing are put under your name.
"I've got Barry John, Phil Bennett and those guys, there."