I have only used the train once. That was enough! Because there is only one platform at Old Trafford, the queues after the game are insane. I don't know if this would affect your shift times or not. The trains are packed also. I had to change trains at Oxford Road for OT. I wouldn't be sure of a DIRECT train from the airport to the stadium, you would probably have to change at either Oxford Road, Piccadilly or Victoria.
My mate has used the metrolink on a couple of occasions. He said that was good, bit of a walk mind, and he didn't catch it from the airport.
You can get to and from OT by train, but i'm pretty sure you would have to change trains at least once. The queues are long also.
I hope this helped!