Dating back to their American Association days (1882-1891) when they were known as the St. Louis Browns, the Cardinals are 70-58 on opening day.
While most of their openers over the years have fallen within the month of April, they have the most success when they don't. Twice in Cardinals history they have started the season in March and they won both games. Early in their history the season started later and four times their first game fell in May. During the fifth month of the year, the Cardinals are 4-1. At 65-57, the Cardinals have a .533 winning percentage in April.
The Cardinals have been involved in 16 opening day shutouts, winning 12 and losing four. They're 20-18 in one-run games on opening day.
St. Louis has played three different Cincinnati clubs on opening day and has success against each of them. The Birds were 2-1 against the American Association Red Stockings, 1-0 against the short-lived American Association Cincinnati Porkers and are 7-4 against the National League Reds.
Some of the teams the Cardinals have fared most poorly against over the years won't be bothering them anymore. The Cardinals were 0-2 on opening day against the American Association Chicago Colts, 0-2 against the Chicago Orphans and 3-4 against the Montreal Expos who are all no more. The Birds are worst against the San Francisco Giants (1-3) and New York Mets (2-4) amongst current teams.
The Cardinals are 6-4 over the last decade on opening day. But they are currently nursing a three-game losing streak with setbacks to Pittsburgh (2009), Colorado (2008) and the Mets (2007.)
How important is an opening day win? The St. Louis Browns, known as one of the worst teams of the modern era, are tied with the Reds and Mets for the most consecutive opening day wins in a row with nine.