With just the Monday Night Football games left to be played, Week 1 of the 2012 NFL season is almost in the books.

A few teams shined unexpectedly in their debuts, while others underachieved. Five favorites lost their opening day games, including the defending Super Bowl champions.

Here are the five biggest stories from the first weekend of the NFL season:

Robert Griffin III

Robert Griffin III had one of the best quarterback debuts in NFL history. The rookie completed 19-of-26 passes for 320 yards and two touchdowns, leading Washington to their first victory of the season.

The Redskins beat the Saints 40-32 in New Orleans. The Saints didn't lose one home game in 2011.

Griffin may have had the best first weekend of any player. He led all signal callers with a 139.9 quarterback rating. He also picked up 42 yards on the ground.

New York Jets

New York arguably had the most dominant performance of any team. The Jets dominated the Buffalo Bills 48-28, in a game that wasn't as close as the score might indicate.

Many experts chose the Bills to pull off the upset, as the betting line moved almost four points in Buffalo's favor up until kick-off. The Jets were in control the entire game, taking a 41-7 lead early in the third quarter.

Mark Sanchez had a career-day, throwing for 266 yards and three touchdowns on 19-of-27 passing. His 123.4 quarterback rating is his best statistical effort of his professional career. New York's defense frustrated quarterback Ryan Fitzpatrick, forcing him to throw three picks, including one that was run back for a score by defensive back Antonio Cromartie.

San Francisco 49ers

San Francisco showed that their success last season wasn't a fluke with their win over Green Bay. The 49ers never trailed in their 30-22 victory at Lambeau Field 

The 49ers defense slowed down a Packers team that had one of the best offensive seasons of all time in 2011. The only time Green Bay was held to less than 22 points in last year's regular season was in their one loss.

Quarterback Alex Smith did more than just manage the San Francisco offense. The former No. 1 overall draft pick threw for two scores and completed 77 percent of his passes.

Peyton Manning

The future Hall of Fame quarterback looked every bit like the Peyton Manning of old in his 2012 debut. He led the Broncos to a 31-19 victory over the Steelers before a national audience on Sunday night.

Manning was extremely efficient, throwing for 253 yards on 19-of-26 passing. It was an almost error-free effort, as the veteran also threw for two touchdowns and without an interception.

The Broncos might be most encouraged by Manning's durability. The quarterback was sacked twice, but played the entire game without incident.

Replacement Referees

After a disastrous preseason, the NFL began the 2012 season with replacement referees. While they got through the Wednesday game between the Giants and Cowboys without much controversy, the same can not be said for Sunday.

While some games had just minor errors, the officials made a few glaring mistakes that received substantial attention. Most notably, the Seahawks were given an additional timeout in their contest with the Cardinals. Arizona ended up winning, but the refs let Seattle call a timeout with 30 seconds left, even though they used their final one when receiver Doug Baldwin got injured.

The officials also made a major mistake in the Sunday night contest. They reviewed a first down call after the ball was snapped on the following play.