The Dolphins' rushing offense was one of the best in the NFL, but the defense held them back from a real playoff push.

After finishing second to the Patriots in the AFC East for back-to-back seasons and missing the playoffs for a fifth straight year, the Dolphins made some big moves last offseason to try to make a playoff push.

Offensive coordinator Mike Sherman was shown the door after only two seasons, and in his place, the Dolphins brought in Bill Lazor to run the offense. They made one of the biggest free agent signings of the offseason, bringing in former Chiefs tackle Branden Albert to anchor their offensive line that gave up the most sacks in the league in 2013. They also brought in Knowshon Moreno to compete for touches in the backfield, and Cortland Finnegan in an attempt to bolster the secondary.

At the end of the day, these changes didn't end up having their desired impact, as the Dolphins once again finished 8-8, missing the playoffs and finishing third in the division.

Let's take a look at what went well and what didn't for the Dolphins this year.

The Good

One of the most encouraging things Dolphins fans can take away from their 2014 campaign is the improvement shown by Ryan Tannehill.

Our Net Expected Points (NEP) metric measures the amount of points a player adds for his team across the season, above or below expectation. Tannehill finished 2014 16th among quarterbacks in Passing NEP and 19th in Passing NEP per drop back (minimum 200 drop backs). While these numbers are far from elite, they show significant improvement from 2013 when he finished 28th in Passing NEP and 25th in Passing NEP per drop back.

Tannehill also posted career highs in completion percentage, yards and touchdowns while putting up a career low in interceptions.

Overshadowed a bit by 2014's historic class of rookie receivers was the performance of Jarvis Landry. The Dolphins second-round pick didn't break records or bring in a lot of highlight-reel catches, but he quietly showed himself to already be a reliable target for Tannehill and flashed the potential to be the top option in Miami if current top wideout Mike Wallace doesn't return in 2015.

Landry finished the year with a Reception NEP of 63.29 which, while only good for 44th in the league, was second on the team, not far behind Wallace's 77.23.

Complementing the improving passing attack, the Dolphins had one of the best rushing offenses in the league in 2014, finishing tied for third in the league in Adjusted Offensive Rushing NEP. Lamar Miller was among the most efficient backs in the NFL, finishing 8th in Rushing NEP and 12th in Rush NEP per carry among backs with 50 or more carries.

On the defensive side of the ball, the Dolphins biggest bright spot was, as it seems to have been for his entire NFL career, Cameron Wake. Wake posted his third 10-plus sack season in five years, recording 11.5 sacks with 3 forced fumbles.

Safety Reshad Jones also had a solid year, recording three interceptions and a sack to go with 70 tackles (second on the team).

The Bad

While there were a lot of positives to take away from the Phins' 2014 season, you don't finish 8-8 without at least a few things going wrong.

Far and away the biggest problem on the offensive side of the ball was the offensive line's struggles in pass protection. Branden Albert was having a solid season, allowing only 3 sacks in 10 games, before going down with an injury. But the rest of the line simply couldn't match his performance. Juwan James gave up six sacks on the year, while Dallas Thomas Thomas and Daryn Colledge gave up seven each. As a team, the Dolphins gave up the fifth-most quarterback hits and the 10th-most sacks. While these numbers are an improvement from 2013, they still border on abysmal and are a clear weak link in the offensive unit.

As a whole, the Dolphins defense struggled. For the second straight year they finished in the bottom half of the league in Adjusted Defensive NEP, falling one spot from 18th in 2013 to 19th in 2014.

While they improved in the secondary, moving from 29th to 21st against the pass, they were still well below average, and it was a case of one step forwards and two steps back, as their run defense, which was top-10 in 2013, fell to 19th.

2015 Outlook

Dolphins fans have plenty of reason for optimism going into the 2015 season. Despite some struggles in 2014, our algorithms gave them a greater than 50% chance at making the playoffs as late as Week 11 this year.

Miami's offense has a real chance to crack the top 10 in 2015, especially if Ryan Tannehill can continue to progress (something the Dolphins seem to believe he will do, as there are rumors of a big contract extension for him.

Landry developing alongside Tannehill will go a long way to getting the passing game going, but if Mike Wallace does indeed leave for greener pastures, Miami will likely need to bring in another weapon, with the alternative being Brian Hartline lining up as their number-two receiver.

While Juwan James was kind of a mess this year, he was also a rookie being asked to start 16 games. If he can develop and Branden Albert can stay healthy, the Dolphins offense should be that much more effective.

On defense, Miami needs to stop taking strides backwards to stop holding the team back. If 2015 sees the defense once again hold the Dolphins back, and maybe even out of playoff contention, defensive coordinator Kevin Coyle may find himself on the way out.

With Buffalo showing signs of improvement and New England a perennial powerhouse, the playoffs won't come easily for Miami in 2015. But with a strong offseason there's no reason to believe they can't make a strong push for it.