I understand the A's wanted a speedy OF, but its not like the Brewers other 4 ML ready OFs were slow. Chourio, Frelick, Weimer, and Mitchell all have great speed and above average defense. I think I would have traded any one of those guys for Contreras (Chuorio would have been tough) to get a already ML C who can hit like Contreras is rare.
FWIW, MLB updated their top 30 prospects. Yeager did not slot (Castaneda slid into the top 30). A's prospects received are Muller (#5), Ruiz (6), Tarnok (11), Salinas (26). So that's quite the haul.