The Super League rivals meet in today’s televised Betfred Challenge Cup third round tie at St Helens with Wakefield looking to earn their first win of the season.
England international Johnstone is fit to resume after coming off with concussion in the first half of their last outing, a 34-6 loss against Wigan Warriors.
He started the campaign with two stunning tries in defeat against Leeds Rhinos and feels back to his best after recovering from two ACL knee injuries.
Johnstone, 25, told The Yorkshire Post: “It’s been a good start.
“I felt good coming off the back of pre-season. It’s taken a while for the knee to feel good again.
“It usually takes about two years. That’s what I found with the other knee. It’s two years to the day actually since the op’ and it finally feels like it’s not an extra body part. It’s part of me again.
“I just feel on the pitch I can do things I want to do now. If I want to step a certain way it’s not a clunky movement. It feels fluent.
“That’s played a big part in how I’m feeling going into this year and the Leeds game went really well for me. It was disappointing what happened against Wigan but now I just want to pick up from where I left off against Leeds and put us on a good Challenge Cup run.”
Catalans have opened with wins against Hull KR and Huddersfield Giants.
Johnstone, who links up for England training on Tuesday, said: “They look class. They are definitely sa top team nowadays and not a team you can take lightly especially Sam Tomkins.
“He’s in quality form and absolutely killing it. He’s probably the most in form player in the comp’ and someone we have looked at this week.”
Johnstone added: “If we can get a good control of him we can get a good foothold in the game and we need our forwards to ramp up against their pack.
“If we can nullify some of those threats we give ourselves a good chance.”
Wakefield were level 6-6 with Wigan at half-time in their last outing.
However, with Johnstone failing to return for the second period from an HIA, they fell away badly with Trinity coach Chris Chester forced into a major reshuffle of his backline.
Johnstone suffered the head injury following a challenge from Willie Isa but said: “I’m fine now.
“I struggled a bit after the game; I lost a bit of memory and couldn’t remember peoples’ names. I felt groggy for a couple of days.
“It’s quite scary. I used to get a bit of concussion when I was younger but I don’t think I’ve had one for over ten years.
“It is frightening but there’s all the right tests in place to make sure you are okay to play.
“I’ve had to pass three tests this week so there’s good safety in place.
“Luckily, with a nine-day turnaround, I was able to do the seven day return to play protocols and passed all my head tests.
“I’m feeling good and ready to go again.”
Support The Yorkshire Post and become a subscriber today. Your subscription will help us to continue to bring quality news to the people of Yorkshire. In return, you’ll see fewer ads on site, get free access to our app and receive exclusive members-only offers. Click HERE to subscribe.