Martin Johnson warned England will be floored by Australia in Saturday's first Test if they cannot learn the lessons from today's 28-28 draw with the Wallaby second-string.
England narrowly avoided a tour-opening defeat after the Australian Barbarians had streaked into a 25-13 lead, courtesy of a hat-trick of tries from full-back James O'Connor.
Number eight Dan Ward-Smith and wing Matt Banahan added to Lee Mears' first-half try and 13 points from Olly Barkley edged England back into the lead.
But Australia fly-half Berrick Barnes drew the scores level with a penalty straight from the restart and England would have lost had his last-gasp penalty attempt not dropped wide.
England tackle the Wallabies in the first of two Tests on Saturday and have another clash with Barbarians to come in Gosford next Tuesday.
"Both camps see this as a four round fight and it is level after the first round," said Johnson.
"We really could and maybe should have won the game at the end with the opportunities we had. Of course, we could have lost it.
"Every part of our game today was good in bits and inconsistent in bits. We did lots of good things but we also compounded a few errors.
"From our point of view it showed that if we do what we say we will, it will work for us.
"But if we relax and make mistakes, miss tackles, get tight defensively and compound errors then it won't.
"If you make mistakes at this level you get punished.
"We gave them too many chances to come back at us. Our defence got too narrow and we paid the price.
"To concede three tries wasn't great but we scored three as well."
Unlike for Australia, where O'Connor's performance has given Wallabies coach Robbie Deans a full-back selection headache for Saturday, Johnson already has his Test team in mind.
Leeds' uncapped flanker Hendre Fourie produced an impressive first-half performance before being replaced but it is unlikely anyone did enough to force their way into the Test XV.
Instead, Johnson will look at this shadow group to improve in time for Tuesday's rematch with the Barbarians in Gosford.
"Some guys played very, very well for almost a scratch team coming together a week off the plane," said Johnson.
"There were lots of real positives. The guys are buzzing with what they can do and how much better they can be.
"We are looking at squad places and Test places far beyond what happens this Saturday."
In contrast, Deans has a major decision to make about whether to start with O'Connor or Kurtley Beale, who scored twice against Fiji at the weekend.
"He couldn't have done much more," Deans said about O'Connor's 25-point performance.
"He had a great game. It's good to have choice. He was assertive in his game. We know he is a talented individual.
"He served his wings well, he served his team well under the high ball and he created a bit himself."