NSW Origin great Andrew Johns has been impersonating Queensland linchpin Johnathan Thurston in an attempt to tighten the Blues' defence heading into State of Origin I.

Johns was heavily involved in putting the Blues through their paces at training on Thursday, slotting in at halfback to run attacking plays as the NSW side focused on defensive structures.

The former champion halfback returned to the Blues fold for the first time since the Timana Tahu racism row in the lead-up to Origin II last year.

Coincidentally, it came on the day Tahu's return to both players' former club Newcastle was announced.

Johns said Blues coach Ricky Stuart had been speaking to him for several weeks about simulating the attacking runs of Thurston and Queensland five-eighth Darren Lockyer.

"I'm just coming to do some work with the halves, just for today, and do a bit of stuff on what Johnathan Thurston and Darren Lockyer do," Johns earlier told the Austereo network.

"(I just thought I'd) come in and just (be) a different set of eyes on what Thurston and Lockyer do and maybe (have) some advice for the halves."

Johns said he had borrowed software from the NRL, used to analyse the strengths and weaknesses of individual players.

"It's phenomenal," he said. "You just put in Johnathan Thurston, all his runs, or Lockyer, all his passes this year, and you go through 400 runs or passes."

The Blues' legend could easily have been mistaken for one of the current players, as he stood at first receiver and deftly offloaded to support including a wide-eyed NSW No.7 Mitchell Pearce.

The Blues' right edge, which includes Maroons target Jamie Soward, was the defensive focus and Johns backed their impressive record for St George Illawarra.

"The players who on their side are defending Thurston are going to be (Mark) Gasnier and Beau Scott," Johns said.

"They've done a pretty good job this year defensively.

"It's just coming in and having a bit of a chat to those guys defending there."

Johns was given the green light to return to the Blues fold by NSW Rugby League boss Geoff Carr, saying he had done his time for a racial slur against Maroons centre Greg Inglis.

Johns was the Blues' saviour in their last series win, when Stuart was at the helm in 2005, making a stunning comeback from a broken jaw after the Blues had been 1-0 down.

Centre Gasnier is the only current player to have been part of that series.

"Joey's football knowledge is second to none," Gasnier said.

"He's great in that regard and he gives a lot of the younger guys confidence, especially in the halves, so he's welcome back from our point of view."

Gasnier, whose partner is due to give birth to the couple's first child any day, said the absence of Test centres Inglis and Justin Hodges from the Maroons side meant little for Wednesday night's Suncorp Stadium showdown.

"They're too good a team," he said.

"While people might see it as a bit of a deficiency in the centres, I don't.

"I think they'll come in and really step up to the mark."

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