Louis van Gaal has voiced his frustration with Martin Atkinson's decision not to award Manchester United a penalty in Monday's scoreless draw with Chelsea at Old Trafford.
The Dutchman feels Atkinson should have pointed to the spot twice, firstly when Willian seemingly handled inside his own area, before Cesar Azpilicueta appeared to bring down Juan Mata.
"I think it was a very good performance, but you have to score a goal and we didn't," Van Gaal told reporters.
"We hit the post twice when the goalkeeper was beaten, then had a big chance in the second half and two penalty cases - one handball and one foul on Mata - but didn't receive a penalty.
"We still don't have the luck we need."
Monday's draw saw United end a four-game losing streak and Van Gaal was pleased with his side's progress after the 2-0 defeat versus Stoke City on Boxing Day, even if they are now eight games without a win in all competitions.
"Against Stoke, I said we didn't dare to play in the first half, but that was entirely different against Chelsea. We dared to play and pressed a lot," he added.
"We were the dominant team, we created chances, we shoot on goal and only gave three chances away. Against a team like Chelsea, with such attackers, that's not bad."
United sit sixth in the Premier League table halfway through the season, nine points behind leaders Arsenal.