Johnstone is set to make his long-awaited comeback from a knee reconstruction when Trinity play host to Championship side Halifax on Sunday in their second pre-season game.
Johnstone was Super League’s young player of the year in 2016 and scored seven tries in 12 appearances last term before suffering an anterior cruciate ligament injury in a home win over Catalans Dragons on April 30.
“He will be like a new signing for us,” Chester said of the 22-year-old flier.
“His form up to getting injured was very, very good and he was on the verge of a mid-season call-up [for England] to play against Samoa.
“It has been a long road for him and we’ve protected him a bit in making sure he got the full nine-month recovery period, but he is in good shape and ready to play.”
Chester said the injury has done nothing to slow Johnstone, who is noted for scoring spectacular long-range tries. He added: “The medical people have done a fantastic job, not just getting him back out on the training field, but also getting him into really good shape.
“He has not lost a yard of pace. One thing he might struggle with at first is the repeat efforts, but I am looking foPeter Smithrward to seeing him play again.”