Ok, we all get the concept. It's the classic Kevin Bacon game with a baseball twist. Not just baseball but baseball cards. I just randomly chose Topps 2011 #135 which happened to be Mike Stanton of the Florida Marlins. I linked him to his 2011 teammate Wes Helms.
In 2002 Helms played for Bobby Cox on the Braves.
In 1969 Cox played alongside Joe Pepitone on the Yankees.
And Pepitone was a member of the 1971 Cubs along with Ron Santo.
Mike Stanton to Ron Santo in 4 degrees of separation.
Leave player suggestions in the comments. All I ask is that they appear on a modern era baseball card. 1950 or more recent.