Two days after the first presidential debate, top aides and people close to Republican presidential nominee Donald Trump admit the candidate's performance was subpar and that he must dramatically improve in his second showdown against Hillary Clinton.

While Trump has been actively spinning his debate performance as a win and insisting that any areas of imperfection were not his fault, his confidants were telling a different story.

The debate was a "disaster" for Trump, according to one source close to the campaign. Also dissatisfied with the debate performance were Trump's children, according to a campaign aide, who said they wish campaign leadership had forced him to take it more seriously.

There's also worry within the family that the campaign is having an adverse impact on their business. Trump's children deny this.

And so does Trump, telling NBC News, "Your sources, if they even exist, are probably sources that have been fired long ago and have no knowledge of what is happening in the campaign. Hard to be unhappy when we are doing so well."

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The internal debate that plagues the Trump campaign surrounds Trump’s public persona. Aides say Trump needs to change. The bombastic candidate that worked in the primary isn't right for the general election. Some aides wish he would reveal the more engaging, kind, and charismatic person they say he is in private.

As for the debates, which showed the looser Trump, two campaign aides told NBC News that Trump didn’t do what was needed Monday night at Hofstra University on Long Island and that the reason is because he did not do enough to prepare for the tedious, one-on-one environment against an experienced and well-prepared opponent.

Related: Poll: Majority Think Clinton Won the Debate

Team Trump scheduled campaign events until two days before the debate and Trump criticized Clinton on stage during the faceoff for hunkering down and leaving the campaign trail to prepare.

Trump aides said that a strategy of winging it will not be the path forward in the Oct. 9 showdown in St. Louis. Instead, they will prepare more traditionally, an aide said, including holding mock debates, honing in on specific policy points and developing strategies to exploit Clinton’s weaknesses. The campaign is even contemplating bringing in a professional debate coach.

Trump’s debate preparation leading up to Monday was minimal. Trump thinks that he performs best when he is unpracticed and he was worried that over-preparation would cause too much pressure and result in him freezing on stage. Advisers and aides, including New Jersey Gov. Chris Christie, Ret. Lt. Gen. Michael Flynn, campaign COO Steve Bannon and aide Stephen Miller, sat in a circle and simply threw questions at Trump to ready him for the first debate.

In post-debate spin, Trump simultaneously declared himself the winner while blaming any imperfections on technical difficulties and moderator Lester Holt of NBC News.

During television interviews and in campaign events Tuesday, Trump highlighted nonscientific and easily manipulated online polls as proof of a successful performance, but his confidantes admit that he did not effectively convey his message and attack Clinton. Trump also said Holt asked him more targeted questions than Clinton and said that he had a defective microphone.

But privately, aides know that — and Trump admits — he doesn't like to lose. Some aides are hopeful this was a wake-up call.

"The best thing about Trump is that he is a fast learner," another campaign source said.

Nobody on team Trump is counting him out and they have high confidence in the candidate.

While the GOP nominee might be able to learn quickly, keeping him focused will be the challenge, the aide said. Trump has a penchant for always being on the go and not delving deep into details, something that is critical when cramming for policy-driven debates. He’s managed to run his entire campaign void of detailed policy prescriptions but his lack of a grasp of details showed Monday night.