Since the surprise announcement of his indictment and guilty plea on Oct. 30, 2017, the short-term, volunteer Trump foreign policy adviser George Papadopoulos has often been described as a central figure in the Trump-Russia affair. Now, a new court filing from special counsel Robert Mueller suggests Papadopoulos was a bit player all along.

Mueller never charged Papadopoulos with any crime involving a conspiracy, or collusion, between the Trump campaign and Russia to fix the 2016 election. Instead, Papadopoulos pleaded guilty to one count of lying to the FBI. He is scheduled to be sentenced Sept. 7.

In preparation, Mueller's office on Friday submitted a memorandum to U.S. District Court in Washington outlining the special counsel's position on sentencing. Although Mueller is adamant that Papadopoulos serve some time in jail — the range for the offense is between zero and six months — the special counsel suggested the final sentence should be just 30 days. As justification, Mueller cited the 30-day sentence given to Alex van der Zwaan, one of the small-time figures caught up in the Trump-Russia probe.

It wasn't the stuff of a "conspiracy against the United States" that Mueller cheerleaders like to cite, nor even of a significant player in the Trump-Russia matter.

Still, Mueller stressed that it was serious business. "The defendant knew the questions he was asked by the FBI were important, and he knew his answers were false at the time he gave them," Mueller wrote. "The nature and the circumstances of the offense warrant a sentence of incarceration."

But how long should that incarceration be, within the zero-to-6 months guidelines? "In order to avoid unwarranted sentencing disparities in similar cases," Mueller wrote, "the government notes that a previous defendant charged by the Special Counsel's Office who pleaded guilty to [making false statements], Alex van der Zwaan, was sentenced to a term of imprisonment of 30 days."

For those who might not remember van der Zwaan, he was a Dutch attorney who worked for the law firm Skadden, Arps in London. Working for Paul Manafort in 2012, van der Zwaan wrote a report clearing Ukrainian president Viktor Yanukovych of blame for jailing his political rival, Yulia Tymoshenko. Van der Zwaan pleaded guilty to lying about his contacts with Manafort and deputy Rick Gates. The case, of course, had nothing to do with any Trump-Russia conspiracy to fix the 2016 election.

Papadopoulos' guilty plea did have something to do with Trump, and with Russia, and the 2016 election. But so far, at least, prosecutors have not laid out any conspiracy between the various elements.

Based in London in March 2016, Papadopoulos, having just learned he would be named to Trump's ragtag foreign policy advisory board, was traveling in Italy when he met a professor named Joseph Mifsud. Mifsud claimed to be well connected in Russia. Papadopoulos saw a relationship with Mifsud as a way to raise his stature among Trump campaign executives, since he had advocated closer ties between the campaign and Russia. Mifsud introduced Papadopoulos to a woman claiming to be Vladimir Putin's niece, as well as to a Russian said to be linked to the Ministry of Foreign affairs. Then, at a breakfast in London on April 26, Mifsud told Papadopoulos he had just returned from Russia and learned the Russians had "dirt" on Hillary Clinton in the form of "thousands of emails."

U.S. officials reportedly learned about Papadopoulos when he told an Australian diplomat about the professor, and the Australian later reported the conversation to American authorities. The Papadopoulos story was reportedly the factor that prompted the FBI to formally begin the Trump-Russia counterintelligence investigation on July 31, 2016.

For reasons that are not clear, the FBI waited until Jan. 27, 2017 to interview Papadopoulos. (The Mueller sentencing memorandum refers to the Jan. 27 interview as "early in the investigation," which seems odd, since at that moment the formal FBI investigation was nearing its six-month point.) In the interview, Papadopoulos told agents about his contacts with Mifsud, but lied about when they took place; he said he first talked to Mifsud before, not after, learning he would join the Trump team of unpaid advisers.

If anyone is an intriguing character in the entire Trump-Russia affair, it is not Papadopoulos but Mifsud. For whom was he working? Who were his contacts? What were his links to Russia, and to the U.S.?

In the sentencing memo, Mueller blamed Papadopoulos for the FBI's failure to fully investigate Mifsud. The memo is the first time the government has publicly acknowledged interviewing Mifsud, and Mueller argued that Papadopoulos' deceptions messed the whole thing up.

"The defendant's lies to the FBI in January 2017 impeded the FBI's investigation into Russian interference in the 2016 presidential election," Mueller wrote. "Most immediately, those statements substantially hindered investigators' ability to effectively question the Professor when the FBI located him in Washington, D.C. approximately two weeks after the defendant's January 27, 2017 interview. The defendant's lies undermined investigators' ability to challenge the Professor or potentially detain or arrest him while he was still in the United States. The government understands that the Professor left the United States on February 11, 2017 and has not returned to the United States since then."

Mifsud was in the U.S. for a meeting of a private group affiliated with the State Department. At the time, he was living in Italy and presumably available and approachable until he disappeared months later, after the announcement of the Papadopoulos plea put his name in the news at the end of October.

One possible problem with Mueller's story is that even after securing Papadopoulos' cooperation, Papadopoulos didn't seem to have much new to tell the FBI. "What's notable here is that, according to the sentencing memo, even after agreeing to cooperate, Papadopoulos provided no substantial information that the FBI didn't already have," Yahoo's Michael Isikoff noted in a tweet on Saturday.

Mueller seemed miffed about that, characterizing Papadopoulos as an unwilling witness. "The defendant did not provide 'substantial assistance,'" Mueller wrote, "and much of the information provided by the defendant came only after the government confronted him with his own emails, text messages, internet search history, and other information it had obtained via search warrants and subpoenas well after the defendant's FBI interview as the government continued its investigation." Mueller was also irritated that Papadopoulos did not tell investigators about a cell phone he used in London until late in the proffer process, although he ultimately handed it over and consented to a search of it.

So it appears Mueller got everything Papadopoulos had. But that is the problem. If Papadopoulos were a key player in a Trump-Russia conspiracy to fix the 2016 election, he would probably have had more to tell investigators. His emails and texts and phone conversations and electronic devices would probably have had more to tell them, too.

But the fact is, Papadopoulos is heading to sentencing on a pretty small charge, facing a pretty light sentence. (If the judge goes along with Mueller's recommendation, that is; Papadopoulos' lawyers will, of course, respond by arguing he should serve no time.) In the end, the man sometimes called a central figure in the Trump-Russia affair did not have a starring role at all.