The Red Devils secured a valiant 1-1 draw with the Bundesliga champions at Old Trafford in the first leg of their Champions League quarter-final last week.
Bayern Munich are a top team and, considering our season so far, I believe that winning would be our greatest-ever achievement in European football
United are set to be without crocked striker Robin van Persie for the return leg on Wednesday night and Wayne Rooney is a serious doubt with a toe injury.
64-year-old Macari wants David Moyes’s side to sit back and defend against the Champions League holders at the Allianz Arena.
“The fact that we conceded an away goal at Old Trafford has made things a little bit more awkward,” Macari told United’s website.
“At some stage in the 90 minutes tonight, we have to score a goal. But I think it would be foolish to open up and try to outplay them, because everything is in their favour.
“They’re on their home ground and they’ll have the most support. I thought our approach at home was right: to sit back and contain them. And I thought Bayern were a little bit cocky on the night, approaching it as if they expected to win.
“But they didn’t, our lads did fantastically well and now we have a realistic chance of pulling off a shock.
“It was a containing job at Old Trafford and I think it’ll be along similar lines this evening, though it will be difficult.
“Bayern Munich are a top team and, considering our season so far, I believe that winning would be our greatest-ever achievement in European football.”
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