Liverpool manager Brendan Rodgers questioned the decision for Manchester United's opening goal in their 3-1 defeat at Old Trafford.
Substitute Ashley Young was brought down by Nathaniel Clyne shortly after half time, and Daley Blind fired the hosts in front from the resulting free kick.
Rodgers' men frustrated United in the opening 45 minutes but Blind's goal opened up the game, and the Liverpool boss questioned the award of the set piece.
"I thought first half we defended well but nowhere near had enough quality and composure on the ball," he said.
"But defensively we weren't bothered too much - any time we were frightened was by our own mistakes.
"We're disappointed with a couple of the goals. I didn't think it was a free kick - I thought Ashley Young bought the challenge.
"Nathaniel Clyne defended brilliantly all day and he's just matched his run. You can see both of them challenging for the ball with their arms and Ashley Young actually jumps on his back.
"So they get a free kick against us, and they work it quite well when they get the goal. But I didn't think it was a free kick."
Liverpool have scored just four goals in their first five games of the season, and Rodgers admitted the lack of chances they are creating is something he will have to address.
"It's something that, over the first five games, I need to look at," he added.
"Is it how we play? Because it's too easy for us at times to play direct into Christian Benteke, who I thought was excellent today.
"You have to want the ball, you have to get on the football to create opportunities.
"I'm lucky because I've got a group that will respond - they work ever so hard, but we have to be technically better than what we've been."