By Matt Hladik We’ve never seen a day like Saturday in college basketball before. The top six teams in the AP top 25 all lost, ensuring a shakeup this week. ESPN’s Basketball Power Index (BPI) has already updated its top 25 following yesterday’s wild slate of results. The BPI sorts teams out by attempting to be the “best predictor of performance going forward. BPI represents how many points above or below average a team is.” Despite losing to Saint Mary’s on Saturday night, Gonzaga remains No. 1 in the BPI rankings. Houston, which actually entered last week as the No. 14 team in the AP poll, i…