A weekly examination of the 49ers' ESPN.com Power Ranking:Preseason: 3 | Last Week: 7 | ESPN.com Power Ranking since 2002The San Francisco 49ers are on a four-game win streak and have moved up a spot in our Power Rankings after being stuck at No. 7 the past two weeks.The 49ers, who were ranked No. 1 in Week 2, fell to No. 10 after losing to Seattle and Indianapolis in back-to-back games.Because of the slow start, the 49ers are stuck behind some teams at the top even though they are one of the hottest teams in the NFL heading into Sunday's game against winless Jacksonville.