Week 3 in the NFL is an interesting week, because it is the first week after which the first teams are basically eliminated from playoff contention. Only three times since 1990 ('92 Chargers, '95 Lions, '98 Bills) has a team made the playoffs after starting 0-3. Since realignment in 2002, not one of the 69 teams that started the season 0-3 made the playoffs, which means the 0-3 teams (Bears, Browns, Jaguars) can start doing mock drafts.
Week 3 is also interesting for teams like the Cowboys that started the season 1-1, because the third game often points such teams in one or the other direction.