This week’s announced departure of four top aides from the de Blasio administration represents the “normal course of government” — not poor morale or skittishness from federal, state and city probes of his fundraising, the mayor said Friday.

Speaking after a news conference on July 4 fireworks security, Mayor Bill de Blasio said “people are thrilled about the stuff we got done” and “there a lot of folks ready to come up from the next layer down and take on bigger responsibilities.”

“I see a very energetic group of people,” de Blasio said of potential replacements for positions like his top lawyer, social-media manager, two senior environmental officials, all positions that saw departures go public over 48 hours.

On Wednesday, de Blasio’s City Hall lawyer handling the administration’s defense to the fundraising investigations, counsel Maya Wiley, said she would leave July 15 to oversee the watchdog agency that handles complaints of NYPD-on-civilian abuse, the Civilian Complaint Review Board, and teach college.

That was the same day news broke that his social-media manager, Scott Kleinberg, announced his resignation on Facebook and called his colleagues “political hacks” led by a “a boss who just didn’t get it.” The next day, Department of Environmental Protection Commissioner said she would retire, and sustainability director Nilda Mesa, said she was departing “to spend time with her family and explore new opportunities.”

“Personnel changes happen all the time,” de Blasio said, adding: “people go into government for a couple years and then go on to something else.”

Last month, de Blasio’s spokeswoman, Karen Hinton, left after a year.

Asked specifically about Kleinberg, who left the Chicago Tribune then quit after less than two months on the job, de Blasio said that his ex-employee “doesn’t seem like much of a professional.”

“Wouldn’t know him from a hole in the wall — and I have no idea what motivates anyone to that early on in a job, leave the job, and then comment publicly,” he said.