The Red Devils lost their second Premier League game in a row on Saturday, as West Bromwich Albion won 2-1 at Old Trafford.
United's next game is against Shakhtar Donetsk in Europe, but Moyes does not believe that his squad has what it takes to go all the way.
"To win the Champions League you have to have five or six world-class players," Moyes told reporters.
"If you look at Bayern Munich, they have five or six really world-class players. Look at Barcelona, who had it in the past, and Real Madrid who have maybe got it now.
"That's the level you have to get at to win it. We've not got that yet. What we have got is experience and several players who are in that category or close to it."
United take on Shakhtar on Wednesday evening.