Welcome to a new MLB series that will be covering a player from the past every Friday. The players who will appear in these articles are not in the Hall of Fame. However, they may have a valid argument as to why they should be enshrined in Cooperstown, or they were just very good players that every baseball fan should know a little about. Thanks to a Twitter poll, Keith Hernandez gets the first write-up. Be sure to follow me on Twitter @jball0202 and vote as there will be a poll each week allowing you to select who the next Flashback Friday article will be about. Hopefully, these pieces will b…