Ruud van Nistelrooy has warned Manchester United they must turn their season around before time runs out.

The United interim manager will take charge of Wednesday’s Carabao Cup encounter with Leicester following Monday’s sacking of Erik ten Hag. United are in discussions with Sporting Lisbon over appointing Ruben Amorim after indicating they will pay his release clause of £8.3 million. Amorim emerged as United’s first choice after a series of talks in recent weeks, with formal negotiations beginning on Monday.

Van Nistelrooy was brought to the club this summer to work under Ten Hag but will assume the first-team coach role until a permanent successor is appointed amid ongoing talks with Amorim.

And the Dutchman, who scored 150 goals and is a firm fan-favourite from his playing days at Old Trafford, said his side must waste no time in getting their campaign back on track.

“As I am sure everyone can imagine, I am writing these notes with a huge amount of mixed emotions,” Van Nistelrooy writes in the match programme ahead of the game against Leicester. “Erik ten Hag brought me back to Manchester United in the summer and, while I have only been part of the coaching staff here for a few months, I will always be grateful to him for giving me the opportunity, and I am saddened to see him leave.

“Even on an interim basis, it is a great honour to manage the club I love for however long I am asked to do so. I can promise that I will continue to give my all, in whatever capacity, to try to turn around our fortunes.

“Despite our results, I am loving being back at Old Trafford and working with the team and staff every day. We’ve seen the squad’s potential at times this season, but clearly not often enough.

“Now is the time for everyone at the club to work together, give everything and turn this season around while we have time. From my experiences as both a player and a coach here, I can say for sure that when players, staff and supporters pull together, Manchester United can be unstoppable.”

Speaking after his team’s 3-1 win over Nacional on Tuesday, when he was given a standing ovation by the Sporting fans, Amorim refused to confirm his intentions as he suggested he has not yet made a final decision over his future. “Manchester United is interested,” he said. “But it’s my choice. Until everything is decided, we won’t be making any noise. It will always be my decision.

“I can’t promise anything. What I know is that I will be at training tomorrow and I will prepare for the game against Estrela Amadora [on Friday]. We have to wait a little bit more, to explain everything I need to explain. Then it will be very clear. It is my decision. I will tell everything.”

United face Leicester before a showdown with Chelsea in the Premier League on Sunday. Ten Hag was sacked this week following a desperate run of one win in eight games in all competitions, leaving United 14th in the Premier League and 21st in the Europa League.