O'Shea sits out Bayern clash after knee op
However, the Republic of Ireland defender is aiming to return in the following two games, when Celtic and AC Milan provide the opposition.
The match at Soldier Field has come a little bit too quickly for O'Shea, who needed a small knee operation in the summer.
He said: "I won't be okay for this first game but hopefully I will be for the other two. I just don't want to push it too much and come back too quickly, especially with the amount of games coming up in August.
"It is going to be an important time and I have to be right."
O'Shea felt discomfort when walking and found out that the injury could have occurred last season.
"They trimmed a little bit off the cartilage and I am told it is as good as new now," he said.
"What the surgeon said to the doctor was that it may have happened during the season. It was something that was waiting to happen.
"I was fortunate it did happen in the summer because it was obviously off-season, no games. So I was lucky.
"It happened while I was walking and I just got it checked out. There was a little problem there."
American goalkeeper Tim Howard has linked up with the squad ahead of the opening game and looks set to start.
Defender Jonathan Spector, 18, could be given a run-out on home soil as some of United's top players are being rested.
Alex Ferguson is hoping the intense pre-season programme, beginning here in America, will kick-start their Premiership season, which begins on August 15.
United are without big names like Ruud van Nistelrooy, Cristiano Ronaldo, Paul Scholes and the Neville brothers Gary and Phil.
Meanwhile, at title rivals Chelsea, Claudio Ranieri has claimed it was him rather than Jose Mourinho who broached the idea of adding Didier Drogba to the star-studded squad.
The Ivory Coast striker joined Chelsea from Marseille this week in a deal which reportedly cost the London club €36.3 million.
Ranieri has revealed how he had advised Russian owner Roman Abramovich to bring Drogba to Stamford Bridge, before the axe fell on him at the end of last season.
"I spoke with Roman to buy Drogba," Ranieri said.
Mourinho, who replaced Ranieri at Chelsea, has followed Ranieri's lead by using Abramovich's millions to form a team which will be expected to challenge for the Premiership and Champions League titles next season.
Mourinho has spoken about cutting back Chelsea's squad to 24 professionals, and he has so far offloaded a number of Ranieri signings, such as Hernan Crespo and Juan Sebastian Veron, who joined AC Milan and Inter Milan respectively on loan deals.
Spending money is not the difficult part of being a Premiership manager, with finding the right blend of players a more significant aspect of the job.
"I spoke a lot about this with Abramovich," said Ranieri.
"I said that it is important the players are a block, that we have a good group together, and that they want to go forward.
"Because if they think that it is an airport, with players coming and going, that is not good.
"It is normal at the beginning that the coach has to think which players can link well and that is very important to make a group.
"But the money is good and it makes the football economy go round.
"I don't know whether players move for the money. I think that it is not right if a man moves only for money, and I don't think this is the case. They want to play, they want to have satisfaction to see how the club is with the coach
"Very few players only think of the money but they are not very good players. Top players will look at the dressing room and everything else."
Now at Valencia, who snapped up the Italian coach when Rafael Benitez joined Liverpool, Ranieri remains a keen observer of events at Chelsea.
"I think that it is difficult to say what Chelsea can do now, but more or less the same as under me," he predicted.
"To win before was not easy but now Chelsea are in a position where there are higher expectations. In the past fourth was fantastic because they were used to finishing sixth, eighth, but now it is different.
"Chelsea will always be among the first group of teams and that is important for the fans and Abramovich's investment."
CONNECT WITH US TODAY
Be the first to know the latest news and updates
