United arrive in town reeling from the revelation that Wayne Rooney wants to leave the club and a poor run of Premier League form that has seen them win just one in four.
The Red Devils did ease some of the misery with a 1-0 Champions League win over Bursaspor on Wednesday night but even that was unimpressive and hopes are high that Stoke can cause a shock this weekend.
The Potters are yet to take a point - or score a goal - from their four Premier League games against Sir Alex Ferguson's side and Coates does not believe they will be any less of a threat this time around.
He told The Sentinel: "I'm not going to speculate about who is or isn't playing for the other side.
"It's not a case of having sympathy with them because of what's happened. This is a tough business.
"But I do know Sir Alex Ferguson is well able to deal with anything that comes his way.
"He has a great track record and this won't be the first issue like this he's had to handle in his career."
Stoke were beaten 2-0 by United at the Britannia last season and Coates is hopeful Tony Pulis' men can put in a better performance on Sunday.
He added: "I thought it was one of our poorest performances. I don't know what happened. But having said that, Manchester United played really well.
"I remember Sir Alex being interviewed later in the season after winning another important game. The interviewer suggested he'd just seen United's best game of the season, but the manager corrected him and said the win at Stoke was the best they had played.
"We were outplayed and it was nothing like the previous season here. We lost 1-0, but I thought we were terrific.
"But sport is unpredictable, things don't always go to plan for one reason and another. You can play poorly and it is hard to say why."