The San Diego Chargers entered the 2015 season looking like they were finally ready to take a step in the right direction.

They stole impact offensive tackle Orlando Franklin from the Broncos in free agency to play alongside D.J. Fluker and King Dunlap, forming a trio of behemoths up front. They selected what looked to be their heir apparent to Ladainian Tomlinson's running back throne by taking Melvin Gordon in the first round of the NFL Draft.

On the defensive end, promising cornerback Jason Verrett, Brandon Flowers, and Pro Bowl safety Eric Weddle were set to anchor a secondary that hoped to compete with the rest of the AFC West.

But then injuries and sub-par play quickly struck the team, resulting in a six-game losing streak early in the year to drop them to a 2-8 record and derail any hopes the Chargers had of making the playoffs.

The team would eventually finish the year ranked 21st in our nERD power rankings, behind all three teams in the AFC West -- including bitter division rivals the Oakland Raiders.

What Went Right

For a team that ended the year with a 4-12 record and finished last in the AFC West, not much went right for the Chargers.

The lone bright spot for the team could be found in their passing game. The Chargers' offense managed to rank as the eighth most efficient passing offense based on our adjusted Passing Net Expected Points (NEP) per play numbers.

Quarterback Philip Rivers was masterful once again in his 12th season in the league; his 0.136 Passing NEP per drop back ranked him as the 13th most efficient signal caller with at least 200 drop backs. While these numbers are certainly nothing to sneeze at -- especially for a 34-year-old quarterback -- Rivers' performance was even more impressive when you consider that his top option in the passing game, Keenan Allen, was lost for half the season with a lacerated kidney.

Before going on injured reserve with this gruesome injury, Allen accrued 67 receptions for 725 yards and 4 touchdowns in the Chargers' first eight games. The third-year wideout flashed his superb talent at times this season, most notably reeling in 12 catches for 133 yards and 2 touchdowns against Minnesota in Week 3 despite being shadowed by Vikings top cornerback Xavier Rhodes for most of the day.

Rivers was also forced to play without tight end Antonio Gates for five games this season. The Chargers' tight end was suspended for the first four games of the year for violating the league's PEDs policy and was hobbled for a number of contests with hip and knee injuries to end the year. Despite playing in his age-35 season, Gates still ranked as a top-10 tight end on a per target basis according to our Reception NEP metrics.

What Went Wrong

Where to begin...

Despite the aforementioned success of Rivers and the passing game, the offense ranked just 19th overall according to our schedule-adjusted NEP metrics.

Much of this was thanks to a rushing attack that was the second-least efficient in the league. The much heralded Melvin Gordon didn't just disappoint in his rookie season; the first-rounder out of Wisconsin was downright awful. Of the 72 running backs with at least 50 rush attempts this past season, Gordon's -0.186 Rushing NEP per attempt ranked him as the sixth least efficient running back in the league.

The Chargers can't lay all the blame on their rookie tailback, however. Gordon was forced to run behind an offensive line riddled with Injuries. Fluker, Franklin, and Dunlap missed four, six, and nine games, respectively, quickly turning a predicted strength for the Chargers going into the 2015 season into one of their biggest weaknesses. As a result, the Chargers surrendered the 12th most sacks in the league to opposing defenses (40) and the sixth most quarterback hits (107).

And things don't get much better when we switch to the defensive side of the football.

The Chargers' defense ranked as the 29th most efficient unit overall, finishing the year 31st and 21st against the pass and run, respectively, in 2015. With the defensive unit ranking in the bottom-12 of the league in sacks, forced fumbles, and interceptions, this group failed to make an impact on the field to help their team win ball games.

What's to Come?

Things look like they may get worse before they start to get better for the Chargers unless they can somehow make a big splash in the draft and free agency.

A number of key players are set to depart via free agency this season, including defensive end Kendall Reyes and Pro Bowl free safety Weddle. Perhaps the best player on a woeful secondary, Weddle is a longshot to return to the team following the huge falling out he and the team had near the end of last season. Beyond Weddle, the team must also find a suitable replacement for oft-burned Flowers to start next to Pro Bowl corner Verrett.

The Chargers have a decision to make on offense with both Antonio Gates and Ladarius Green set to hit free agency.

Going into the 2015 season, our own Joe Redemann deemed Green a work-in-progress, and even with another underwhelming season under his belt -- his 0.62 Reception NEP per target ranked him as the 13th most efficient tight end with at least 50 targets, just behind Eric Ebron and Clive Walford -- it doesn't look like that outlook has changed much, if at all. And while Gates seems intent on re-signing with San Diego, the soon-to-be-36-year-old is not the future at the position the Chargers are looking for.

The one silver lining for the Chargers may be the fact that they own the third overall pick as well as selections in the second, third, fourth, sixth, and seventh rounds in the draft so far this year. With so many needs, however, the Chargers will need to use each pick wisely if they hope to climb the rankings in an AFC West that has two playoff teams sitting at the top in the 11-5 Kansas City Chiefs and the 2015 Super Bowl Champion Denver Broncos.