Hence Lancaster's realistic assessment that Sunday's 28-9 winning performance will not be good enough to beat the Wallabies in what is a dry run for the all-important pool match at next year's Rugby World Cup.
"Definitely, we need to step up from that to beat Australia," Lancaster said, all too aware that England did not score a single point after the 52nd minute.
"It is not good enough, not converting chances. You have got to make sure you take them. That is another step we need to take. The win will relieve some of the pressure, but we will be pretty disappointed with some elements of the game, and we know that we need to improve to beat a quality side like Australia."
That quality is relative, given that the Wallabies have also lost two of their autumn tests, against France and Ireland. These are not the All Blacks coming to Twickenham, but as Australia showed in their 23-26 defeat in Dublin, there is a slickness and cleverness to their back play that is beyond the scope of England.
Sure, there were flashes of top-end quality, the wraparound Ford-Owen Farrell ploy that teed up the first of May's two tries, the neat chip-kick right from Ford that found the impressive Watson, who off-loaded to Mike Brown for his try and, for once, the neat inter-passing of forwards and backs that led to the final try.
Ticks in boxes on that front.
However, the fundamental failings were more disturbing. Why did England pick a kicking combo at 10-12 in Ford and Farrell, and then not kick, all the more so when it was wet, with burly opponents lining up the meat-and-drink tackles? Where was the tactical acumen? Why not play the ball deep in those early stages?
Instead, it was flick-flick passing, quick 22 drop-outs that led to turnovers, and not a shred of evidence of rugby grey matter being applied. Factor in, too, that Samoa cleverly held off committing to the ruck, so that they could sneak round and sack the halfback, with England looking baffled. Why not pick and go, or maul to drag in the fringe defenders?
Lancaster put the strategic misreading down to "youthful exuberance".
England certainly have to find a way to shed their anxiety. They looked angst-ridden and uncertain in those early stages, stumbling and fumbling rather than playing a simple, straightforward game.
And yet. This victory might just be balm to frayed nerves. Defeat would have been a calamity and thrown the entire Lancaster project into doubt. If England launch their World Cup next September with a comparable win over another of the Pacific Island teams, Fiji, then it will be considered a decent opening gambit.
By then, Lancaster can expect to see Ford bedded in to the No10 slot, with the prospect of some real thunder in midfield in the shape of Manu Tuilagi and perhaps Sam Burgess to feed off his sharp-eyed passing.
Ford looked the real deal. If anything it was his ability to withstand a battering that indicated that the 21-year-old will be here for the long haul. His physical stature has often been cited against him making it. No more. He took his hits but bounced off the turf to come back for more.
Alongside him, Farrell had another mixed afternoon, but the die has surely been cast for the Wallabies game. If Lancaster had wanted to check out his options for next week, then he ought to have given Billy Twelvetrees longer than 15 minutes.
England's chariot is back on the road, if only clunking forward.