Looking back on the Falcons’ season, some of the factors that led to their free fall from atop the NFC to last place in the NFC South with a 4-12 record included injuries, coaching/medical decisions, lack of depth and lack of proven talent along the lines of scrimmage.

The Falcons won’t publicly acknowledge the injury factor, which included 11 players going on injured reserve. The IR list includes several key starters, such as wide receiver Julio Jones, offensive tackle Sam Baker, linebacker/defensive end Kroy Biermann and, late in the season, defensive tackle Corey Peters.

“You can’t make injuries an excuse,” Falcons coach Mike Smith said.

Both lines were a problem after key veterans John Abraham, Todd McClure and Tyson Clabo were released in the offseason. Their replacements didn’t match or surpass their predecessor’s level of play, and it appears that the position coaches were fired for the under-performance of those replacements. The Falcons declined to comment about the firings.

“I believe that you have to control the line of scrimmage,” said Smith, before firing offensive line coaches Pat Hill and Paul Dunn and defensive line coach Ray Hamilton. “If there is one thing that stood out this year is that we did not control it on both sides of the football.”

There also was Smith’s dubious decision to allow Tony Gonzalez to take leave from the team during training camp and the decision to play Roddy White as a decoy with a high ankle sprain.

Collectively, all of the factors led to the downfall of a team that widely was considered a Super Bowl contender.

The collapse was historic.

Since the NFL began to seed playoff teams in 1975, the Falcons became the third team to go from a No. 1 seed to a last-place team the next season. The 2003 Raiders and the 2005 Eagles had similar falls. The Raiders haven’t been to the playoffs since, while the 2006 Eagles bounced back with a 10-6 record before losing in the division round of the playoffs.

“There are a lot of changes to be made and adjustments to be made and considered,” Falcons general manager Thomas Dimitroff said. “We believe that we have a talented football team here and that we need to make adjustments. We will talk about those as well, but I really truly believe that we have the nucleus, the coach and the leadership to turn this around quickly.”

Here are the Falcons’ final grades for 2013 season:

Quarterback: Matt Ryan became the team's all-time leading passer, while playing behind a makeshift offensive line. He was sacked 44 times, hit 100 times and hurried on 206 plays. On 38.4 percent of the pass attempts, his pocket was compromised. He threw a career-high 17 interceptions and had four of them returned for touchdowns. Backup Dominique Davis played 12 snaps against Tampa Bay before he was knocked out of the game and Ryan had to return. Grade: C-plus

Running backs: Steven Jackson never got going and dropped too many passes. He was hailed as a pass-catching threat, but he showed that only sporadically. Jackson, who missed four games with a hamstring injury, rushed 157 times for 543 yards and six touchdowns. He turns 31 in July. The Falcons finished last in the NFL in rushing, averaging 77.9 yards per game. Jacquizz Rodgers and Jason Snelling were steady in reserve roles. Antone Smith was dazzling when got touches. Grade: D

Wide receivers/tight ends: The unit's production was compromised as they never worked together during training camp. When Gonzalez was on leave, Julio Jones had a hamstring injury. When Jones got healthy and Gonzalez was set to return, White went down with high ankle sprain. Instead of going with Harry Douglas and Drew Davis, the Falcons used a hobbled White as a decoy. Gonzalez got into groove with a 12-catch game vs. New England in Game 4. White, who suffered a subsequent hamstring injury favoring the ankle, didn't get healthy until the Falcons' record was 2-9. Douglas posted his first 1,000-yard season and led the team with 85 catches. Undrafted rookie Darius Johnson pitched in with 22 catches. Grade: C-plus

Offensive line: Center/guard Peter Konz and tackle Lamar Holmes, the central figures in the line rebuild, had tough years. Konz, a second-round pick in 2012, gave up six sacks, three hits and 33 hurries, according to profootballfocus.com. Holmes, a third-round pick in 2012, gave up 10 sacks, 13 hits and 53 hurries. Left guard Justin Blalock was the only player with a stable grade in pass protection. The entire unit struggled with run blocking. Ryan Schraeder, an undrafted rookie from Valdosta State, got some valuable experience late in the season and looks like a keeper. An experienced NFL offensive line coach likely will be added to whip this unit into shape. A top draft pick and/or strategic free-agent signing will add to the competition. Grade: F

Defensive line: The unit ranked 31st against the run giving up 135.8 yards per game. The Falcons had only 32 sacks, tied for 30th with Houston. Only Jacksonville (31) and Chicago (31) had fewer. Grade: F

Linebackers: Sean Weatherspoon had a very tough year physically. Undrafted rookies Joplo Bartu (789 snaps) and Paul Worrilow contributed heavily. Bartu was strong against the run and has speed to improve in coverage. Veterans Akeem Dent and Stephen Nicholas were demoted and may not figure in the team's future plans. Grade: C

Defensive backs: The play of rookie Desmond Trufant was one of the bright spots. He was one of 10 rookies picked in the first round to play more than 1,000 snaps. Rookie Robert Alford, the team's second-round pick, showed flashes. Safety William Moore kept things together, while Thomas DeCoud's level of play dipped. Robert McClain finished strong at nickel back after a bumpy start to the season. Veteran Asante Samuel ended the season on the bench. Grade: C-plus

Special teams: Kicker Matt Bryant made 34 of his 35 field-goal attempts. Punter Matt Bosher averaged 41.1 net yards on his punts. The kickoff-return team averaged 24.4 yards per game. The team went through three punt returners before going with the steady McClain. Grade: B

Coaches: The coaches had a tough year. Offensive coordinator Dirk Koetter had to come up with game plans that tried to hide the line's deficiencies and was minus key weapons throughout the season. Defensive coordinator Mike Nolan showed the patience of Job while playing with as many as six rookies at times. Specials-teams coordinator Keith Armstrong's unit was solid and came up a few of the season's spectacular plays, such as Snelling's onside-kick recovery at San Francisco. The penalties rose dramatically from 69 to 104, and the team finished 24th with a minus-7 in takeaways. Grade: C

GAME BALLS

Offense: Ryan played 1,088 snaps, mostly under great duress, and performed admirably considering the circumstances. Defense: Worrilow played 790 snaps and led the team in tackles. Special teams: Smith was a tackling machine in coverage.

NEXT UP

Falcons coaches will coach at team at the Senior Bowl, along with the staff from Jacksonville. The team’s offseason program starts April 29, with the draft set for May 8-10.