What do BBC Sport's player ratings mean?

For some of the biggest football matches we cover, BBC Sport's football reporters will be giving their views on how each player performed using a sliding scale of 1-10.But what does each rating mean?10 - What a performance. Probably a match-winning display, maybe a wonder goal, hat-trick or something that has set a new record. These will be rare and reserved for the truly outstanding efforts.9 - Excellent. Probably scored at least one, or created a goal, or produced an outstanding defensive/goal