Sunday's Clasico between Barcelona and Real Madrid could be decided by any number of different factors.
There might be a red card. A ball could hit the post for Barcelona and bounce out; a ball could hit the post for Real Madrid and bounce in. Barca's high-press under Hansi Flick could overwhelm a Madrid side that couldn't handle it last season. Or Barca's high-press could fall apart the way it did against Sevilla a few weeks ago.
Perhaps Madrid's more controlled tactics under Xabi Alonso will frustrate the chaos Barcelona typically likes to create.