The Italian striker looked sharp and levelled the scores nine minutes from time but Jesse Lingard's dismissal for handball allowed Tadanari Lee the chance to notch his second spot-kick of the game two minutes later. Johnstone pulled off a fine stop but, in truth, the Reds should have been comfortably ahead despite a goalless first half.
"It was very frustrating because we came here to win," Macheda told MUTV afterwards. "I think we played much better than them but we missed a lot of chances - myself as well.
"I can't believe how we dropped points in this game as I think we did very well. The referee gave them two penalties and I don't know what to say, it was just very frustrating for us as we had to win this game. We're very disappointed to go back home with just one point.
"We could have scored even with 10 men but it was a good performance and I think the lads enjoyed this game. I'm looking forward to the next match [the last group fixture at second-placed Aston Villa] as it'll be crucial to us. We need to win that game to get through to the second group."
Macheda is in great shape ahead of the trip to the Midlands next Monday, with the action again live on MUTV, but the qualification picture for the elite phase is a little complicated. A win would take United above Villa but they still have another fixture to play - against Tottenham. There is a slot open to the best third-place side which takes Group 3 into account. Chelsea are in that position with 18 points and better goal difference so a draw would be insufficient for the Reds.