United opens its Group A campaign at home to in-form Leverkusen tomorrow, when Shakhtar - eliminated in the last 16 last season - travels to Sociedad.
"I think all groups are tough," Moyes said on Monday. "You could always pick the winner out of it in the past, but it's become more difficult and more unpredictable now. I see it as a pretty tough, open group. Everyone wants to do well in it. This is a competition that the players are used to and enjoy playing in."
The English champions are favored to top the group, but their start to Moyes' first season in charge has been underwhelming.
After picking up four points from its opening three games for the team's worst start to a Premier League campaign in five years, United toiled on Saturday to a 2-0 win over promoted Crystal Palace, which played with more than half of the game with 10 men.
However, Moyes did see both Robin van Persie and Wayne Rooney get on the scoresheet against Palace. And with Rooney back in action after a head injury and getting closer to full fitness, opponents should be fearful of United's front two.
"The hope is that we get a partnership where folk are saying, 'My goodness, we are having to play against Robin van Persie and Wayne Rooney,'" Moyes said. "Everybody is looking to see if those two form a partnership that can score lots of goals."
The match against Palace was marred by controversy after Ashley Young was booked for diving, sparking a debate with calls from the London club chairman Steve Parish for players who dive to be shown straight red cards.
"You can never be sure it won't happen again but I have had a word with (Young) privately," said Moyes. "I said after the game and I have said for many years diving is something we should have retrospective video for. That would help referees no end. It is really difficult at times. Moving from Everton to Manchester United doesn't change my views on that."
?Leverkusen has never won in England in eight attempts but has started the German league season with four wins from five matches, and has a coach in Sami Hyypia who knows United well.
Hyypia spent 10 years in the Premier League with Liverpool, winning the Champions League with the club in 2005.
"We shouldn't go out with too much respect," the former Finland defender said. "I hope my players don't just look around at a stadium rich in history and get autographs from Rooney.
"They do have a new coach, but they play the same football. Man United are a great team. They won everything in the last 10 years. But to give up already before the game, I won't do that. Otherwise we could send out our second team."
Leverkusen beat United in the Champions League semifinals in 2002 on the away-goals rule, then lost to Real Madrid in the final.
Socieded has had a mixed start to the season, with only one win in the Spanish league through four rounds. It did do well to dispatch French side Lyon in the Champions League playoffs, however, to earn the club only its second appearance in the competition's group stage.
Shakhtar has lost three of its best players from last season's run to the knockout stage, with Fernandinho (Manchester City), Willian (Chelsea, via Anzhi Makhachkala) and Henrikh Mkhitaryan (Borussia Dortmund) all moving on. The team is fourth after nine games in the defense of its Ukrainian title.
- AP
