The phrase "season average" means the typical or normal level of something that is observed or experienced over a particular period of time, usually a full season. Full definition
Over a whole season an average of one goal a game would give us just 38 goals. (westhamway.net)
Last season he averaged 1.5 key passes per game, while he made six assists thanks to his great touch on the ball and vision on the field. (russianfootballnews.com)
He also shot 30 percentage points better than season average on 3's Yeah... he played above his head, and kudos to him for doing it. (sbnation.com)