Ralf Rangnick is optimistic it will not take too long for Manchester United to become a force again in a new era under Erik ten Hag.
Ten Haag will leave his role as Ajax head coach to take over from interim United manager Rangnick at the end of the season.
The Dutchman faces a rebuilding job, with United only sixth in the Premier League and set to miss out on Champions League football after falling short of expectations again this season.
It is five years since the 20-time champions of England last won a trophy and Rangnick previously stated that the club need "open-heart surgery" in order to turn their fortunes around
Rangnick, who will take over as Austria coach but is due to remain at Old Trafford in a consultancy role, says he has not yet spoken to Ten Hag since the Ajax coach was appointed as his successor.
Ahead of Monday's Premier League encounter with Brentford, the 63-year-old told Sky Sports: "I'm pretty sure he's [Ten Hag] got my phone number!
"He's got another couple of games to play with Ajax, we have another three games to play here. Whenever he wants to speak with me and exchange our opinions, I'm more than happy to do that."
Rangnick believes the next man to take the United hotseat can be successful in the not-too-distant future if the club learn from their mistakes and recruit wisely.
He added: "Knowing Erik will be the manager, with a good recruitment process and bringing in the right players, I'm very positive the supporters and the media will be able to see a better team and, at the end, hopefully a better position in the league.
"There are quite a few good examples in the league with when Jurgen Klopp came to Liverpool, Pep Guardiola to Manchester City, Thomas Tuchel came to Chelsea – yes, he came in the middle of the season and inherited a top-quality squad, but you still need to win the Champions League.
"If you know what you're looking for, the profiles of the different positions you need, it shouldn't hopefully take too long."
Rangnick has no idea what part Cristiano Ronaldo will play under Ten Hag, though.
He added: "This is a question you need to ask Erik ten Hag.
"He's showed that he can still be a vital part of this team, but it's obvious the team needs some more strikers. There should be two or three new strikers next season, it's pretty obvious."