The Swansea City fullback was left frustrated after quickfire goals from Robin van Persie and Danny Welbeck gave the Red Devils control of the season-opening fixture.
Robin van Persie and Danny Welbeck netted in quickfire fashion, as they set the champions on their way to a 4-1 win in David Moyes's first league game in charge.
Wilfried Bony fired a consolation goal home for the Welsh side on his Premier League debut, but it ultimately counted for little, with both United scorers netting again either side of the new man's strike.
"Obviously we're disappointed," Rangel told the club's official website. "We hadn't lost a game up until now, including preseason, so sometimes it's a good thing to have a result like this.
"It was two minutes of madness, really, and it ended up changing the game.
"If they hadn't scored the second goal, then I think we would have had a chance in the second half. That killed it, really, but we gave it everything and we have to accept the defeat and move on.
"It puts things into perspective, because we have to get used to losing as well as winning."
Michael Laudrup's side next faces Romanian outfit Petrolul Ploiesti for a place in the Europa League group stage, and Rangel is hoping for a good performance in order to put their heavy loss behind them.
"Thursday's game will help us forget the defeat and it is one of those games that we want to win at home," Rangel said. "I thought we played well [on Saturday] and created lots of chances, but they were clinical and the finishing was the difference in the end."