"It's going to be a competitive tour from a selection perspective and the fly-half position will be absolutely no different," said Jones, who starts tonight's domestic encounter from the replacements bench.
"Ronan is playing very well and he is a quality player. It will be a big challenge to try and oust him."
Jones says that tonight's game is another chance to impress Lions coach Ian McGeechan, although experience tells him that the best place to catch McGeechan's eye is on the tour itself.
"I'm delighted to have been selected for my second tour and I know it will be a challenging trip.
"We've a few domestic games left and I've got a job to do with the Scarlets. The only thing you can do is prepare to the best of your ability.
"But once the tour starts it's all about trying to focus on your own game because selection is out of your control.
"There are only two specialist fly-halves going and it will be interesting to see what the coaches plans are.
"They will want to build and develop a game plan and as an outside-half it's important you become comfortable and accustomed with that because you have to help implement it on the field.
"That will be the first challenge and then you have to try and bring your own stamp on things. Hopefully that will be enough for me."
Whether or not he does earn the No10 shirt ahead of his 2005 and now 2009 Lions rival, Jones believes the Lions squad as a whole has what it takes to overcome a huge obstacle in the form of the world champion Springboks.
"It's a massive challenge and doesn't get much harder than beating the world champions in their own backyard. But we can beat South Africa.
"It's a Lions squad full of talent and ability. Hopefully we can do the Lions shirt justice."