After sitting on the bench for most of the season so far, veteran 1B Jason Giambi has the first three-homer game of his career in the Rockies’ 7 – 1 win over Philadelphia. He hits homers in his first three at-bats, driving in all 7 of his team’s runs, but fails in his last two at-bats to become only the 16th player to hit four dingers in one game. Giambi entered the game hitting .115 with 1 homer and 4 RBI; at 40, he is the second-oldest player to hit three home runs in a game, after Stan Musial who was 41 when he accomplished the feat on July 8, 1962.

On May 19, 2011 — After sitting on the bench for most of the season so far, veteran 1B Jason Giambi has the first three-homer game of his career in the Rockies’ 7 – 1 win over Philadelphia. He hits homers in his first three at-bats, driving in all 7 of his team’s runs, but fails in his last two at-bats to become only the 16th player to hit four dingers in one game. Giambi entered the game hitting .115 with 1 homer and 4 RBI; at 40, he is the second-oldest player to hit three home runs in a game, after Stan Musial who was 41 when he accomplished the feat on July 8, 1962.

Source:
Baseball Reference May 19