system (noun): a set of connected things that form a complex whole, especially
1. a set of things that work together forming a complete mechanism or network (eg the state railroad system, a car's braking system)
2. a set of organs in an animal or plant with a common function (eg the respiratory system)
3. a complete animal (or human) body (eg "The police doctor found drugs in his system")
"to get something out of one's system" is used in sense 3 above, eg:
- literal, we need to get cholesterol out of our system
- figurative, get love out of our system (broken heart), get worry out of our system (anxiety) etc
In your quotation, it looks as though Player has got a girl, or feelings of love, out of his system.