It took just minutes for Robert Mueller's testimony before the House Judiciary Committee to turn into a painful exercise when it became clear the 74 year-old special counsel had difficulty handling the questions posed to him about his long, complex investigation into the Trump-Russia affair.

Mueller was slow to react to questions. He frequently asked for questions to be repeated. He sometimes appeared confused. He did not appear to be conversant with some issues in the investigation. He did not, or could not, put together detailed answers even to those questions he agreed to address.

Reporters who have covered Mueller for years saw differences from his appearances in the past. "I haven't seen a performance quite like this from Mueller," the New York Times' Noah Weiland said in an online discussion. "In 12 years as FBI director, he gave plenty of clipped responses. But more often than not he was more rhetorically agile than anyone on the committees that were questioning him. And there was rarely a time when he even paused for a second after a question was asked. There was little searching in his eyes for answers. He rarely looked at notes."

[Read: Mueller unfamiliar with key parts of own report]

That was the Mueller of years ago. On Wednesday, Mueller seemed incapable of engaging fully with the questions that were presented to him.

"This is delicate to say, but Mueller, whom I deeply respect, has not publicly testified before Congress in at least six years. And he does not appear as sharp as he was then."

Mueller's performance raised questions that reached far beyond one appearance before one committee. It called into doubt the degree to which Mueller was in charge of the entire special counsel investigation.

"You wonder how much of this was affecting the investigation," one Republican member of the House said as he watched Mueller's testimony. "It sheds a lot of light on what happened the last two years. He wasn't in charge."

If Mueller was not fully in charge, that would direct attention to the staff he assembled for the investigation — staff that President Trump has often derided as "17 angry Democrats." Some of Mueller's aides were Democratic donors, and a key aide, Andrew Weissmann, famously attended Hillary Clinton's 2016 election night event that was planned as a victory party. It seems likely that Republicans will direct new attention to them in light of Mueller's appearance.

No one noticed Mueller's performance that more than the centerpiece of the investigation, the president himself. "This has been a disaster for the Democrats and a disaster for the reputation of Robert Mueller," the president tweeted — not his own words, but those of Fox News anchor Chris Wallace during a break in the testimony.

During that commentary, Wallace said Mueller "has seemed very uncertain with his brief. He doesn't seem to know things that are in the report ... I think it does raise questions about the degree to which he actually was in charge and control of this [investigation]."

[Also read: MSNBC host: Mueller sounding 'old and feeble' helps Democrats]