The NFL's most disappointing team is ...

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Dallas Cowboys head coach Jason Garrett said Monday that his team “didn’t do a good enough job” this season. The Cowboys finished the season with a 4-12 record, their worst since 1989, when they finished 1-15 in Troy Aikman’s rookie season.

Injuries to star players such as Tony Romo and Dez Bryant played a big part in the Cowboys being the most disappointing team of 2015, according to ESPN’s Power Panel.

They entered Week 1 sixth in the NFL but fell an NFL-high 24 spots over the course of the season to wind up No. 30 heading into the postseason. The Baltimore Ravens (18-spot drop) and San Diego Chargers (15) fell the furthest after Dallas.

No help behind Romo and Bryant

The reasons for the disappointing season start with Romo’s injuries. Romo played 115 snaps in Weeks 1 and 2 before suffering a broken clavicle. He returned to play 101 snaps in Weeks 11 and 12 before re-injuring the collarbone.

Dallas is 16-16 over the last two seasons, but the Cowboys' record varies dramatically depending on who’s playing quarterback.

In the 19 games Romo has started over the last two seasons, the Cowboys are 15-4. Dallas is 1-12 during that span in games started by Brandon Weeden, Matt Cassel or Kellen Moore.

Romo’s Total QBR of 78 since the start of 2014 is the highest in the NFL among qualified quarterbacks. All other Cowboys quarterbacks have combined for a QBR of 31. That is five points lower than the Jacksonville Jaguars, who have the lowest QBR in the NFL over the last two seasons.

With Bryant out or injured most of the season, Cowboys wide receivers combined to catch 12 touchdown passes. Bryant alone caught 16 last season while all other Dallas wideouts had another 12.

The lack of a solid backup plan at quarterback and wide receiver led to the Cowboys ranking 31st in the NFL in points per game at 17.2. They ranked fifth in points per game in 2014 at 29.2.

Ground game not missing Murray

While Cowboys backup quarterbacks struggled, the dropoff in the ground game from DeMarco Murray in 2014 to Darren McFadden and others in 2015 was not very drastic.

In fact, the 2015 Cowboys matched last season’s averages in yards per rush (4.6), yards before contact per rush (2.7) and yards after contact per rush (1.9) within a tenth of a yard.

By comparison, Murray averaged 3.6 yards per rush, 2.1 yards before contact per rush and 1.5 yards after contact per rush with the Philadelphia Eagles this season. Murray had the benefit of Dallas’ offensive line helping him gain 2.8 yards before contact per rush in 2014.

Other notes

The biggest power rankings risers from the preseason to the end of the regular season are the Washington Redskins (21-spot jump), Carolina Panthers (18) and New York Jets (14).

Three teams are who we thought they were: The Pittsburgh Steelers (No. 7), St. Louis Rams (22) and Chicago Bears (25) wrapped up the season in the same place they started.