This thread is based on the completely wrong assumption that YPG measures passing defensive performance. Factors such as opponent offenses performance, number of plays ran, opponents running more could all explain the difference. If you check DVOA rating which controls for opponent strength and measure the performance the whole defence not just passing: http://www.footballoutsiders.com/stats/teamdef Ravens is 20th the full season, and 18th when more recent games are considered ( see weighted DVOA ). There is no dramatic turn around. Even if you don't like DVOA, passing yards allowed is still a meaningless stat. If the opponents chose to run more due to early leads, or Pees sell out to stop the pass, you will get lower passing yards numbers. Any stats that doesn't factor in run-pass strategies are pointless. My guess is that the less yards allowed in the second half is mostly due to less passing plays. Best lies are made of stats, you can easily fool yourselves if not careful. That's why stats are for losers.