Flacco is tied for the league lead in throws that go more than 20 yards downfield with Tom Brady and is second in percentage of passes of that length. However, he's only 20th in completion percentage on those passes. The Sun expands on how his efficiency on deep balls has declined as the team's performances have gotten worse:
In the first month of the season, the Ravens led the NFL in passing plays that gained 20 or more yards. But they only produced six such plays in the past three weeks, and four came in the Week 6 win over the Dallas Cowboys at M&T Bank Stadium. In the 30-point road loss to the Houston Texans in Week 7, quarterback Joe Flacco didn’t complete a single pass that traveled 10 or more yards down the field, according to ESPN Stats and Info.
The Ravens started out 3-1, and although they've only lost one game since, that was the blowout loss to Houston, while the two wins were by a combined five points, including an ugly 9-6 win over the lowly Kansas City Chiefs.
It seems unlikely the Ravens will stop throwing deep: Torrey Smith is a potent downfield threat when he's playing well, and Flacco is better known for his arm strength than his accuracy on short passes. However, the numbers show that how well he throws it have a major effect on whether or not his team wins.