The Dutch international has been nursing a groin injury he suffered in training recently which forced him to miss United's shock 4-1 defeat by Manchester City in a dramatic derby encounter last weekend.
Moyes had hoped to have Van Persie, the leading scorer in England last season with 30 goals in all competitions, available for the visit of Liverpool. Now Moyes has said the 30-year-old is poised to miss the match, and is doubtful for the defending champions' forthcoming Premier League match against West Bromwich Albion.
"I don't think he'll play," Moyes told a news conference on Tuesday. "But I think he has an outside chance for Saturday." Moyes admitted the manner of his side's 4-1 thrashing by City, his first derby since succeeding Alex Ferguson as United manager, had left him stunned.
"It shocked me, but when you're a football manager for the length of time I've been you are always going to have shocks," Moyes said. "But it's gone now so I can't do anything about it," the former Everton boss added. "You can't dwell too long on it. We're looking to get the next game started and trying to win.
"It's always a big game whenever you play any cup tie, but especially I think when you play Liverpool against Manchester United. It maybe takes on a bigger significance than people would expect. In recent years the League Cup has been seen as a 'development' competition by managers of leading English clubs, who've often rested their first-choice players for more important Premier League or European assignments.
But the City result has given Wednesday's match a different context for many United fans and Moyes acknowledged the conflicting interests surrounding this particular clash with Liverpool. "I think my idea was always to focus on every competition," Moyes explained.
"It's always been (the mentality) here to win. I do think the Capital One (League) Cup is a route to give as many young players an much opportunity as we can. "The draw sometimes in the competition gives you reasons to do that. But obviously this is a really big tie that came out of the hat first.
"I'm still getting to know all the players here and how they react to situations. I'll get the chance to know a few more of them this week. "Hopefully, they will show me what they can do." Liverpool have Luis Suarez available again now the Uruguay striker has served his 10-match ban for biting Chelsea's Branislav Ivanovic last season.
Suarez's previous matches against the 'Red Devils' include a racism row with United defender Patrice Evra in 2011. But Moyes tried to play down the importance of Suarez's anticipated return on Wednesday by saying: "I think it means Liverpool have got a really good player back. "Does it change the complexion? I don't know. I'm not looking at Liverpool too much except that the qualities of Luis Suarez are very good."
Meanwhile, Moyes refused to comment on claims made Tuesday by Real Madrid president Florentino Perez that United made a late bid to derail the Spanish giants' signing of Gareth Bale, for a reported world transfer fee, from Tottenham Hotspur. "If I was I wouldn't tell you," said Moyes. "We don't talk about it. "We only talk about the players we think there is a reason to talk about and I wouldn't comment on that."