Blanco was signed by the Dodgers in November 1989 - there are members of the 25-man roster for the Diamondbacks who weren't even born then (Chris Owings and Randall Delgado, to be precise), but it was a long path to the majors. He got a cup of coffee with Los Angeles in 1997, but it wasn't until two years after that he became a regular, playing 88 games for the Colorado Rockies. All told, he played for 11 different teams in his career, his four years with the Cubs from 2005-08 being his longest tenure with any franchise. He spent 2011 and 2012 with Arizona, and made a bid for the backup catcher role this spring, losing out to Tuffy Gosewisch.
His longevity is particularly surprising, considering the toll of his position, with catching generally considered the most physically demanding, particularly in terms of knees and backs. Last year, Blanco was the oldest catcher in the majors, and it wasn't even close. The next-oldest, Jose Molina, was born almost four years after Blanco. Henry reached the post-season three times, with Atlanta in 2002 and Minnesota in 2004, as well as with us in 2011, but never finished on the winning side in a series. He finishes with a .994 fielding percentage, tied for 16th on the all-time list - and that's tied with Yadier Molina, giving some idea how reliable Blanco has been.
Presuming he will become the assistant hitting coach to the Diamondbacks, this will likely mean Mark Grace goes back to the minor leagues to work there. However, I get the feeling that, the next coaching opportunity which opens up, will probably have Grace's name on the shortlist.
Update. This is odd. The original press release sent out by the team said, "Veteran catcher Henry Blanco announced his retirement from professional baseball today, and was subsequently added to the D-backs' Major League coaching staff." But the one currently sitting online says, "Prior to tonight's game, the D-backs released catcher Henry Blanco from his Minor League contract, and was subsequently added to the D-backs' Major League coaching staff." I don't think it makes too much difference: either way, I suspect Blanco has played his last major-league game. Unless Gosewisch (or God forbid, Montero) gets hurt, then maybe he comes back from the dugout?