Conversation so far:
in regards to jason giambi, what was the colorado rockies about?
Looking for a veteran bat to help their playoff push, the Rockies agreed to a deal with Giambi on August 23, 2009.
was that successful?
On May 19, 2011, against the Philadelphia Phillies, Giambi hit three home runs in one game, the first such game for him of his career.

Question: who did giambi play against that day?
Self-contained rewrite: who did giambi play against on May 19, 2011?