Alex Ferguson called on his Manchester United side to improve their penalty-taking after Wayne Rooney missed their fifth spot-kick of the season.
United, who have won the Cup a record 11 times, did advance in this term's FA Cup with a 1-0 third-round replay against West Ham at Old Trafford thanks to Rooney's early first-half goal.
But the England striker wasted a chance to put the result beyond doubt when he blazed over a penalty 12 minutes from time.
That was Rooney's second penalty miss of the season, with Robin van Persie, Javier Hernandez and Nani also proving fallible from 12 yards out this term.
Ferguson wants to see United enjoy better penalty returns, even though they are at the top of the Premier League table, seven points clear from last year's champions, Manchester City.
"It's not 'one of those things'. We have to improve," said Ferguson, United's manager. "There's talk of the boy [Rickie] Lambert at Southampton, he's scored 33 out of 33. That's what penalty-kick taking is all about.
"There's been several great penalty takers over the years, [Matt] le Tissier [the retired Southampton star] got 47 out of 48," he said. "There's a player in Scotland who played for Rangers who got 57 in a row. Your penalty kicks are to take advantage of whether it's a handball or a foul and score a goal."
Despite the miss, United still came through unscathed as Rooney, in his first appearance since injuring his knee in training on Christmas Day, scored in the ninth minute after a superb ball from Anderson sent Hernandez clear down the left-hand side.
The Mexican forward then unselfishly crossed for Rooney who slid in to tap the ball into an empty net for his 10th goal of the season.
United defender Rafael could have given away a penalty in the opening moments of the second half when appeared to use his arm to control the ball but referee Phil Dowd was unmoved.
Dowd did point to the spot when United great Ryan Giggs' cross was blocked by Jordan Spence's hand in the box, but Rooney scuffed the penalty over the bar, looking at the turf as Ferguson turned away in disgust.
However, West Ham manager Sam Allardyce was even more frustrated with the referee as he gave voice to the widely held belief within English football that officials favour Ferguson's men when United are at home at Old Trafford.
"I'm very disappointed we are not given a penalty for Rafael's handball which is blatant and clear for the referee to see," he said. "He couldn't find the courage to give it, they go down the other end and the same happens to Jordan Spence. The lack of consistency is a real frustration.
"The referee needs to make the right decision. We got an opportunity to get to 1-1 which we deserved."
United will now face Fulham in the fourth round at Old Trafford as they look to win the FA Cup for the first time since 2004.
Meanwhile Ferguson praised Giggs's impact on Wednesday's match and backed the 39-year-old to play for another season, despite the midfielder claiming he will not make a decision until the end of the current campaign.
"He'll play for another year, his quality is still there," Ferguson said of Giggs. "He has the appetite for it, he's just a fantastic human being."