A native of Drytown, California, he was signed by Boston out of the University of San Francisco.
Giannini was a major leaguer whose career, statistically speaking, was only slightly different from that of Eddie Gaedel or Moonlight Graham.
He appeared in one game and hit a double in two at-bats for a .500 average, without runs or RBI.
As a fielder, he collected two assists and committed two errors for a .909 fielding percentage.
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