Louis van Gaal has issued a warning that Manchester United should no longer be expected to win consistently.

United exited the Champions League this week following a 3-2 defeat to Wolfsburg and a 0-0 draw with West Ham has left them three points behind Premier League leaders Leicester City ahead of this weekend's games.

Van Gaal has drawn criticism for his side's languid style of play and lack of attacking vigour this season, with many citing the combination of success and exciting football delivered by Alex Ferguson as proof the Dutchman is not the right man to continue at Old Trafford.

While the former Bayern Munich boss accepts there are certain games this season where he has failed to mastermind the results expected, he has pointed to the strengthening of the Premier League as proof that demanding constant victories is simply unrealistic.

"When you say that I am hired to make the difference, you are right. I don't think it is [completely] like that – I can make the difference, in tactics and everything, but I cannot score goals," he said.

"They say a club like Manchester United has to win. That's the past. You have to analyse the club now. Now we have much more clubs who have money… also the structure and are able to win something.

"Next year, all the clubs in the Premier League have a bigger budget than most in Europe. That makes a big difference. Every club can also buy a player. You think Manchester United has a lot of money – that is true, but other clubs are asking for much more from us than from Bournemouth.

"The difference is not so big any more. The confirmation is every week. The bottom clubs can beat the top teams. There is no other league where that happens as often as it does in the Premier League. It is very difficult for a Premier League club to match with the other leagues in the Champions League. It was not so easy for all the clubs to qualify themselves.

"You shall always say a club like Manchester United shall go further than the group stage. Okay. I think the same but the reality is that is not happening."

Van Gaal is adamant, however, that he is the right man for the job as he looks to sustain a serious title challenge this term.

"I don't have any doubts. You can lose and you can win in sport, and you have to accept that, as a player and as a manager," he added.

"I have read already in the media that I am 64 and I am too old. I read the same things 20 years ago. I cannot change what is in your mind. I can only say the facts."