The Foxes confirmed last Friday that they had handed a two-and-a-half-year contract to the Dutchman after parting ways with Steve Cooper.
Van Nistelrooy was in the stands at the Gtech Community Stadium on Saturday afternoon as Leicester succumbed to a 4-1 defeat to Brentford in West London.
With Premier League fixtures taking place in midweek, it is a quick turnaround for Van Nistelrooy and his squad of players as they prepare to take on West Ham United at the King Power Stadium.
Just five points separate the two teams in the Premier League table, upping the stakes ahead of Van Nistelrooy's first game in charge.
Van Nistelrooy reveals Maresca discussions
As recently as the start of last month, it became public knowledge that Van Nistelrooy and Maresca - the former Leicester boss now in charge of Chelsea - were friends away from the pitch courtesy of their spell with Malaga during their playing days.
The pair played out a 1-1 draw when Van Nistelrooy was in caretaker charge of Manchester United on November 3, and the 49-year-old has now revealed that the occasion represented one of several times where Maresca has spoken fondly of his time in the Wast Midlands.
Speaking to reporters at a press conference, Van Nistelrooy said: "When the first approach was there, you are going to think about the club, the setup, the players, the training ground.
"You're curious about the people who work there and Enzo [Maresca], being a great friend and former teammate, he was the first one to call. What better information could I get?
"When we played against each other in the Premier League - when I was Manchester United interim boss against Chelsea - we spoke for half-an-hour.
"I didn't know yet about Leicester but we spoke about it and he was already very positive [after managing them]. That only got better when I spoke to him. I have to say he was absolutely right, according to first impressions."
Key period for Van Nistelrooy
Keeping Leicester outside of the relegation zone for the remainder of the season will be Van Nistelrooy's primary objective, and the result against the Hammers on Tuesday night could set the tone.
Leicester face a testing fixture list during the remainder of 2024, playing Brighton & Hove Albion, Newcastle United, Wolverhampton Wanderers, Liverpool and Manchester City.
Aside from the home showdown with Wolves, Leicester will be regarded as clear underdogs, and points may realistically be required versus West Ham to give them some breathing space.