Sir Alex Ferguson has admitted that English sides will not be able to underestimate the group phase of the UEFA Champions League in future as the number of wealthy investors getting involved in other countries continues to increase.
There is only one round of matches to go before the line-up for the last 16 is finalised, and so far Arsenal are the only Premier League team to have secured their passage.
Manchester City's fate is no longer in their own hands, while Manchester United and Chelsea face nervy final group games against Basel and Valencia in midweek.
Ferguson recognises that European football is becoming ever more competitive, with clubs outside of the more famous leagues rich enough to attract top playing talent.
"It's true we could have only one team through, and it represents a different challenge for English clubs," said Ferguson.
"There are clubs around Europe with a lot of money behind them. Maybe we need to raise our game a little bit and not underestimate the group stages.
"There's maybe a little change when you see the money that Russian teams have got and the Brazilians that are playing for them.
"Even a club like APOEL Nicosia have got (money) to bring in foreign players.
"Wealth is playing a part in that respect."
Ferguson remains confident that United will make it through to the knockout phase, as they have a one-point lead over Group C rivals Basel ahead of Wednesday's trip to Switzerland.
"The advantage I see for us is that they need to win," said Ferguson
"At some point - though I'm not sure it will happen immediately - they'll have to try and beat us."