And then there was one.

The San Francisco 49ers entered Week 9 as one of two remaining undefeated teams left the NFL. They exited Thursday night's clash with the Arizona Cardinals boasting an 8-0 record.

Now, they stand alone as the NFL's only perfect team.

That's because the Baltimore Ravens (6-2) were able to do what seven teams (the Jets have played New England twice) before them have been unable to accomplish — knock off the defending Super Bowl champion Patriots (8-1). The Ravens, just three-point underdogs heading into Sunday night's matchup, won the home game by a score of 37-20.

The 49ers begin the second half of their schedule, which is considered to be significantly more difficult, with a Monday night matchup at Levi's Stadium against the Seattle Seahawks on November 11 (find tickets). They also host the Green Bay Packers and Los Angeles Rams, and travel for games against the Ravens, New Orleans Saints, and Seahawks during the weeks leading to the end of the regular season.

San Francisco will also be getting several injured players back in the coming weeks, with November 11 returns likely for most (maybe all). Those players are both starting tackles, Joe Staley and Mike McGlinchey, fullback Kyle Juszczyk, and cornerback Ahkello Witherspoon.

Of course, the team found out this past week that starting linebacker Kwon Alexander has been lost for the year due to a torn pectoral muscle.

It will be interesting to see how the Patriots' first loss of the season impacts power rankings and media perception during the coming week. New England has been the consensus No. 1 ranked team for the entire season. The 49ers have managed to climb into the top 3 in most power rankings.