New Manchester United manager Ralf Rangnick said he has never seen a player as physically fit as Cristiano Ronaldo following his two-goal display in the 3-2 win over Arsenal in the Premier League.

Rangnick was unveiled as United's interim manager at a news conference on Friday, with the German appointed until the end of the season following the sacking of Ole Gunnar Solskjaer.

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There have been questions raised over whether 36-year-old Ronaldo will fit into Rangnick's high-pressing style and the Portugal captain was dropped to the bench last weekend for the 1-1 draw at Chelsea.

But Rangnick, who was in attendance at Old Trafford on Thursday as caretaker boss Michael Carrick took charge for the final time, said he was impressed by Ronaldo's performance against Arsenal and it will be his responsibility to get the best of the former Real Madrid and Juventus star.

"You always have to adapt your style or your idea of football to the players you have available, not visa versa," Rangnick said.

"Having seen Cristiano yesterday in the second half at the age of 36, an amazing top professional. At his age, I've never seen a player who is still that physically fit. He's still a player who can easily make the difference. So yes, it's about how we can develop the whole team, not only Cristiano.

"We play in the most competitive league in the world so we need all the players on board. What I saw from Cristiano yesterday, he is more than willing to do that, to put his input into the team. His teammates will have to do the same."

Ronaldo surpassed 800 career goals in Thursday's victory over Arsenal and is United's top scorer with 12 goals so far in all competitions.

Regarded as the "godfather of gegenpressing," Rangnick inspired a generation of German coaches, including Liverpool manager Jurgen Klopp and Chelsea counterpart Thomas Tuchel.

The 63-year-old has taken the reins until the end of the season and is then set to begin a two-year consultancy role in the summer.

When asked whether there was scope to continue as manager if things go well, however, Rangnick said he could "recommend" that he carries on.