Tim Sherwood reflected the sense of chaos and upheaval at Tottenham Hotspur when he said that he did not know whether he would take charge of the team at Southampton on Sunday, after his managerial debut ended in a 2-1 Capital One Cup quarter-final defeat by West Ham United.

The club's youth co-ordinator, who was elevated on Monday morning to the post of caretaker manager after André Villas-Boas's sacking, said he would love to be considered for the position on a permanent basis.

The club are casting for a big-name appointment, with Frank de Boer of Ajax prominent on their wish-list. De Boer would be loth to leave Ajax before the end of the season, as they chase a fourth consecutive league title, and many of Tottenham's other targets are in similar situations. Sherwood, though, admitted that his club have to act decisively.

"The players are professional enough to get on with it and I've just tried to steady the ship," Sherwood said after his team blew a lead by conceding twice in the last 10 minutes. "There's obviously upheaval when your manager leaves … you've been used to him and his voice. It's a new voice now. It would be good to get it resolved for the football club's sake and the players'."

Sherwood said he took a call from the chairman, Daniel Levy, on Monday at 10.15am and it set in motion what has been a whirlwind few days. "He asked me to take the first-team training, which I did, and here we are now," Sherwood said. "The future beyond that … I need to have a chat with the chairman and see what they're thinking. I don't know, to be honest. The immediate future is up in the air, that's as much as I know. Do I know about Southampton? No.

"It's been different. It's madness, really. I'm not used to sleeping two hours at night. I'm waking up thinking about footballers. I said the other day, I slept like a baby – I woke up crying four times in the middle of the night.

"I'm up for a challenge, I always have been. I'm very opinionated. I know a certain way that I need to play. I think I can manage men, deal with them, be honest with them. The decision that's going on is out of my hands unfortunately. I've got to be in the frame but it's not my decision."

Sherwood changed the team's style from that of Villas-Boas, playing with two strikers and a higher tempo. But they flagged in the final 20 minutes which, in part, allowed West Ham to come back to win. Sherwood suggested the players were not fit enough to play in that style.

"I think, to be honest, they ran out of a bit of steam," he said. "I think they are fit enough to play a certain way but I wanted to change the way we wanted to play.

"The problem we had was giving the ball away. There was a period after we scored [in the 67th minute] when we were turning over possession and it's impossible to rest when you are out of possession. You need to rest on the ball and they need to recognise when is the right time to do that. I don't think they did that well enough, and that encouraged West Ham.

"I think they are fit enough but to play a certain way … When it's a complete change of mindset of how I asked them to play – I asked them to go a bit more gung-ho, and up and at them. You need to acclimatise to that."

Sherwood described the defeat as a major disappointment and said that everybody in the dressing room was "sick". But for Sam Allardyce and West Ham, it was a night of glory, with his side's two late goals setting up a semi-final against Manchester City. They had won at White Hart Lane in the Premier League on 6 October.

"It's a brilliant effort from the squad and a great night for the fans," Allardyce said. "It's twice on the trot now and I know how much it means to them. It was a case of exploiting the spaces Tottenham left when they got 1-0 up.

"I thought they might have sat back and protected that, but they didn't. They went for the second … and we started exploiting the spaces that were left."