Matthew Stafford had his most intercepted passes per game played with 3+ games played in a season in his rookie season in 2009, with 2.

against which opponent does matthew stafford have the most career interceptions per game with at least 3 games played
Interpreted as:
against which opponent does Matthew Stafford have the most career passing interceptions per game in a regular season with at least 3 games played
StatMuse has season-level data for intercepted passes going back to the 1932 season.