Kirby Lee-USA TODAY Sports

In 2012, the San Diego Chargers failed to reach the playoffs for the third straight year under Norv Turner. So, the team fired their head coach and hired Denver Broncos offensive coordinator Mike McCoy to come in and fix the Chargers offensive woes.

The offense that McCoy is inheriting was poor in 2012 across the board. Last year, San Diego was ranked No. 31 overall, averaging just 297.3 yards of offense per game. The running game was ranked No. 27, averaging only 91.3 yards per game, while the passing attack was ranked at No. 24 overall, averaging 205.9 yards per game.

In 2012, the Chargers scored 21.9 points per game, which was No. 20 in the NFL.

The next-to-last ranking in 2012 is a shocking testament to how badly things deteriorated under Turner. To think that back in 2010, San Diego was the No. 1 overall offense in the NFL, averaging 395.6 yards per game. That year they averaged 27.6 points per game.

Rivers was the No. 2 ranked passer in the league, with a score of 101.8, behind only Tom Brady. Rivers threw for 30 touchdowns compared to just 13 interceptions that season.

That offense had multiple weapons in Antonio Gates, Vincent Jackson and Darren Sproles. When you remove talent like Jackson and Sproles, your overall production is bound to suffer.

To this day, Rivers still has his favorite security blanket in tight end Gates. Gates has been slowed by various injuries over the years, most notably turf toe. But he is still there, and as long as Rivers has Gates to bail him out, the Chargers offense begins with those two players.

What caused the Chargers offense to drop so much in 2012?

1) One of the most alarming statistics of the 2012 season is that Philip Rivers was sacked 49 times. Only Aaron Rodgers was sacked more, and that was 51 times.

Rivers wound up throwing 26 touchdown passes to 15 interceptions in 2012, which is an improvement over 2011, when he threw 27 touchdowns compared to 20 interceptions. By the way, he was only sacked 30 times in 2011, which means that the offensive line gave up an additional 19 sacks last year.

In 2012, Rivers was ranked No. 11 in the NFL with a passer rating of 88.7. The year before, Rivers was again ranked No. 11 in passer rating with an almost identical rating of 88.6. But the passer rating index has its share of flaws, which are brought to light when we use other indexes.

If you switch over to the Total QBR Index instead, we find that Rivers was ranked No. 31 overall in 2012 with a score of 40.6. Over at Pro Football Focus.com, Rivers ranked No. 28 overall for quarterbacks in 2012, as he finished with an overall negative grade. In 2011, Rivers was No. 11 in Total QBR, with a score of 62.7, so his game plunged noticeably in the last year.

2) In 2012, the Chargers lost leading wide receiver Vincent Jackson to Tampa Bay and tried to replace him with free agent Robert Meachem. San Diego signed Meachem to a four-year deal for $25.9 million, of which $14 million is guaranteed.

Meachem was a epic fail for San Diego, as he only caught 14 passes out of 32 targets. He scored two touchdowns and gained just 207 yards on the entire season.

Meachem is guaranteed to earn $5 million in 2013, which is just one more reason why A.J. Smith is no longer employed as the general manager in San Diego.

3) San Diego assumed veteran starting tackle Jared Gaither knew by now how to play through some pain. Gaither was another blunder by Smith, as he gave the tackle a four-year deal for $24.6 million, of which $13.5 million was guaranteed.

Gaither would sit out games unless he was feeling 100 percent healthy, which is a rare occurrence for anybody in the NFL. It is even more rare if you are an offensive lineman.

Gaither alienated teammates with his attitude, and it would not be a surprise if the team released him this offseason, despite the guaranteed money and the ensuing salary cap hit ($6 million hit for 2013 season).

You can attribute the Gaither mess as a painful memory and parting gift from the legacy of A.J. Smith.

4) Another factor was a fairly significant drop in the running game, specifically Ryan Mathews. In 2011, Mathews was the No. 10 running back in the NFL, as he gained 1,091 yards, scored six touchdowns and averaged 4.9 yards per carry.

In 2012, Matthews dropped down to No. 27 in the league, gaining only 707 yards and his average lost more than a yard, down to 3.8 per carry. He only scored one rushing touchdown on the year.

When your running game is struggling so much, that puts more pressure on your quarterback to carry the team. But when your quarterback is being sacked 49 times, it is hard to sustain that many drives when you are laying flat on your back.

So, what does Mike McCoy have to do to fix the Chargers offense?

1) Improve the overall quality of talent on the offense. Pro Football Focus.com ranked every starter on the Chargers compared to their peers around the rest of the NFL. There were only two players that finished with a ranking in the top 20 last year. They were G Louis Vasquez (No. 13) and Ryan Mathews (No. 16).

That means that the Chargers have to upgrade across the board via free agency and the 2013 draft. The Chargers come into the 2013 offseason $8.7 million under the salary cap. That won't be enough to fix all the problems, but it is a start.

McCoy will need to determine what the returning players do best and tailor a scheme and design plays that cater to their skills. It's not like McCoy hasn't done it before, as he has dealt with a wide range of personnel at Denver that ranged from quarterbacks Peyton Manning to Tim Tebow to Kyle Orton.

2) Give Ryan Mathews some help with another capable back. In 2012, the Chargers were hoping that adding backs like Jackie Battle and Ronnie Brown would be sufficient to take away some of the stress of carrying the bulk of the workload from Mathews.

It didn't pan out very well, so it is back to the drawing board for San Diego. To think that they used to employ Darren Sproles in that capacity two years ago. Ugh.

3) Give Rivers a good QB coach to work with. The Chargers hired Frank Reich to serve as Rivers' quarterbacks coach. Reich has worked with the likes of Peyton Manning and has been around some outstanding offenses during his tenure as a NFL quarterback and a coach.

Reich is the author of two of the greatest comebacks in football history (Buffalo Bills vs. Houston Oilers in 1993 and Maryland Terrapins vs. Miami Hurricanes in 1984). No doubt Reich would have been able to get Rivers' attention when the Chargers were up 24-0 at home against Denver and wound up losing the game 35-24.

4) Improve the offensive line play and don't let Louis Vasquez leave in free agency. As bad as the Chargers offensive line was in 2012, they have to find a way to keep Vasquez in San Diego.

Granted, there are only so many talented guards in free agency this year, so if the Chargers allow Vasquez to test the market, he will undoubtedly get bowled over by a contract offer the team can't afford to match.

San Diego needs to scour the college ranks for offensive-line help, whether it is with draft picks or bringing in undrafted rookie free agents. They really don't have that much salary cap space to do much in free agency, so they will have to rely on their scouting department to turn over some rocks.

5) Develop young key wide receivers such as Vincent Brown and Danario Alexander. Brown was a local star at San Diego State in college and showed promise as a rookie. Unfortunately, Brown was hurt in 2012 and missed the entire season due to the injury.

He will be looking to break out in his third year removed from college, so if he can produce what Robert Meachem was supposed to provide, that would be big plus for Rivers.

Alexander wound up with career highs across the board in receptions, yards, touchdowns, average yards per pass and first downs. He is a restricted free agent and should be brought back for another year.

6) Cut down of the number of sacks that Rivers takes. This is one area where new offensive coordinator Ken Whisenhunt has to step forward and make an impact.

If there is anybody that can appreciate how damaging sacks can be it is Whisenhunt, who watched his Arizona quarterbacks get sacked 58 times, the most any team suffered in 2012.

Whisenhunt and Frank Reich need to determine if Rivers has to release the ball sooner, take fewer steps in his dropback, or if the team has to run shorter pass routes. If the pass protection can't hold up for at least three to four seconds, then there is only so much the coaches can do to help Rivers.

7) Take better care of the football. In 2012, the Chargers wound up with a ratio of plus-two. The offense turned it over 26 times but were bailed out by the defense coming up with 28 turnovers. In 2011, the Chargers gave the ball up 28 times and wound up with a minus-seven turnover ratio.

That is a function of Rivers making better decisions with the football. It also is a reflection that when your quarterback is hit that many times, there are going to be some fumbles that go along with the high number of sacks.

There is a need for a serious influx of better talent on the Chargers offense under McCoy. The team owns the No. 11 overall draft pick in the 2013 NFL draft.

In their latest computer-generated mock draft version at Draftec.com, they awarded the Chargers with Alabama guard Chance Warmack in the first round.

If San Diego can bring Vasquez back and pair him up with Warmack, that would be a great start in re-establishing a solid offensive line.

But there is still an awful long way to go for McCoy to get this unit back to a No. 1 ranking. Thanks for checking out the presentation.