Yes, making a simple copy of the files that comprise a Virtual Machine is one way of backing it up. Just do it with the Guest OS shutdown, not suspended and VMware Player closed.
You can also use the Snapshot feature to revert to a previous state thus resolving the immediate issue however remember to always keep any User Data that's stored with the Guest OSes Filesystem backed up so you do not loose and User Data when having to restore a Virtual Machine from the backup copy or reverting to a previous Snapshot.