Even the best in the world have an off day.
Nobody's perfect, and when you're an NFL quarterback—arguably the most difficult position in team sports—there are going to be games where you don't throw for the number of touchdowns you want. Or the number of yards you want. Or you throw too many interceptions.
Or you go 1-11 for zero yards in a 37-0 loss to the Jets.
These things happen, even to the best signal callers on the planet. Don't remember the time Tom Brady threw four picks in a 31-0 shutout L to the Bills? Scroll and learn some history.