He has four years of evidence his coaching staff has compiled about players' work under pressure, skills, fitness, compatibility and ability to deliver the game-plan England want as they host the eighth RWC.
Lancaster has tried 71 players in 41 tests with a 60 per cent success rate. It is not a massive endorsement of their work and England have drawn the most awkward pool with the Wallabies, Wales, Fiji and Uruguay in their group.
Those twin facts have quickened the pulses of all who support the Red Rose's ambitions.
Loose forward Chris Robshaw will lead the squad. He and many others who lost to France in Paris were part of a flat performance, especially at the breakdowns where they were indecisive and penalised heavily.
That lacklustre production may have been caused by their heavy training workload, including a recent visit to the States where they were put through a special fortnight camp in Colorado.
Once the squad is announced tomorrow, they will begin to sharpen and taper towards the World Cup.
They still have concerns about the lack of accurate grunt at hooker and in midfield without Dylan Hartley and Manu Tuilagi, while there were some disconcerting lineout wobbles in Paris.
However England play three of their pool games at Twickenham where their supporters, and familiarity with all that comes with massive internationals at the famous venue, will give them some advantage. Maybe not much, but as we hear from coaches these days, the one per centers are what make the difference.
England begin their tilt at the Webb Ellis Cup on September 19 against Fiji at Twickenham before they meet Wales and the Wallabies at the same venue then finish their pool games against Uruguay at Manchester.
