Majority of the time. Your screwed. But that isn't your fault. so blame your fellow defenders and halfbacks that arent getting back
That's actually not really that true. I play centre defence and sometimes my fellow defenders are still at half-way (yes I do yell at them but in the nicest way possible) so it ends up being "two attackers against me the lone centre back", I know that they want me to try to attack the one with the ball so he can pass it to the other thus beating me and giving them a good chance for a clean shot on goal.
Since they want me to come up and attack what I do is pretend I am running up to attack the guy with the ball, making him pass but then what I do is intercept the pass and get the ball, get it up to the mids and yeah...
Sometimes this won't work and u will have to do this but it reuqires speed so if ur not fast u may wanna brush up on ur spped because if ever u r faced with a situation where this is the only thing left to do, then u won't get anywhere without speed.
Basically what u want to do is recover from what has just happened and try to chase after the guy with the ball, by this time the coach will be probably yelling at the other defenders to get back so if they are back they could help u out if the guy passes the the other attack etc. Well if u do get close and have a chance at winning it try cutting him off or slide tackling him.
hope it helps