Bando is a classic case of the underrated player. He played a crucial defensive position, but it was not shortstop or second base (the Hall of Fame has quite a few flashy 2B's who had not so great bats). He was excellent at that position -- but he was not Brooks Robinson. He had very good mid-range power, but he was not Reggie Jackson. He drew a tremendous number of walks, but nobody pays attention to that. If you take the whole deal, he was a hell of a player, quite comparable to other 3B's and the occasional 2B who is underrated and whom the Hall of Fame voters have ignored: Ken Boyer, Graig Nettles, Buddy Bell, Bobby Grich.
Baseball Reference rates Sal Bando as the 16th most valuable 3B of all time. I think that the top 20 at each position (the top 80 among pitchers) warrant membership in the Hall -- certainly a lot more serious consideration than Bando ever got. He was booted off the ballots after the first year, gaining only 3 out of 413 votes. But when I look at the list of players on that ballot in 1987, I see quite a few Hall of Famers whom Baseball Reference rate as at best Bando's equal in value, no more: Jim Bunning, Catfish Hunter, Tony Oliva, Orlando Cepeda, Bill Mazeroski.
Those A's teams had other guys who have been underrated, but who were terrific: Bert Campaneris, Gene Tenace. Dick Williams was a jerk, but he knew talent when he saw it.