March 11, 2015 was a huge day of celebration for the Miami Dolphins. There were smiles aplenty from owner Stephen Ross and the front office, led by vice president Mike Tannenbaum, as the team signed the biggest free agent in franchise history -- Ndamukong Suh -- to a six-year, $114 million contract with $60 million in guarantees. At the time, the contract was an NFL record for a defensive player.

Suh was expected to be the cornerstone of a newly dominant defense in South Florida. Terms such as “greatness” and “dominance” were being thrown around by the Dolphins’ brass on that memorable day. However, Suh was wise to curtail expectations with some of his first comments to the Miami media two years ago.

“This is the ultimate team sport,” Suh said at the time. “There is no way I can do it by myself."

Those words ring very true in retrospect. Despite adding Suh two years ago, Miami’s defense remains near the bottom of the NFL.

The Dolphins were ranked 29th in 2016 and 25th in 2015. Even more baffling is that they were 30th and 28th against the run, respectively, the past two seasons. The Dolphins were 12th in total defense in 2014 before Suh’s arrival, leading optimism that Miami could field a top-five unit and immediately end its lengthy playoff drought. Instead, the Dolphins went 6-10 in Suh's first season before last year's 10-6 record and first playoff berth since 2008.

As we recently passed Suh’s two-year anniversary of signing with Miami, this is an ideal time to reflect what has gone wrong. Should the blame fall on Suh? Or are the Dolphins to blame for not building a better defense around the Pro Bowl defensive tackle?

According to statistical analysis and opinions of personnel executives around the NFL, it is the Dolphins who haven’t held up their end.

Suh, 30, remains a dominant force among defensive tackles. According to ESPN Stats & Information, Suh leads all defensive tackles in total snaps (1,838) and batted passes (11) and is second in tackles (133) and tackles for loss (38) in the past two years. Suh also is durable and has never missed a game in his career due to injury. He missed two games in 2011 via suspension while with the Detroit Lions.

These numbers suggest Suh is still performing at an elite level, especially considering he’s constantly fighting through double-teams and not getting nearly enough help from Miami’s defensive teammates, especially at the linebacker and secondary levels.

Dolphins coach Adam Gase and others within the organization have consistently pointed out that Suh is holding up his end of the bargain and is the least of the team’s worries defensively.

“Suh, I don’t need to talk about him,” Gase said recently at the NFL combine. “Because he’s probably the best in the business.”

ESPN.com reached out to two NFL personnel executives on opposing teams to get a non-biased take on Suh. Both were adamant that poor overall defense – not Suh -- was to blame for Miami’s troubles.

One personnel source pointed out that it is relatively easy to scheme around three-technique players, which is how Suh is primarily used in Miami’s defense. Opponents can attack the edges in the running game instead of running up the middle or can double-team Suh with the guard and center in the passing game, especially if other areas of the defense are weak.

That often was a strategy used by Miami’s opponents, which relied on other players around Suh to step up and win one-on-one matchups. Pro Bowl defensive end Cameron Wake, for example, took advantage and got 11½ sacks in a bounce-back year coming off a season-ending Achilles injury. But many other players on Miami’s defense did not.

Another good example is Kansas City Chiefs defensive tackle Dontari Poe. Poe’s numbers (26 tackles, one sack) last season didn’t match up to Suh’s (72 tackles, five sacks), but Poe is considered among the NFL’s top defensive tackles. Similarly, Kansas City’s defense struggled overall and was ranked 24th last season and 26th against the run. Defensive tackle is one of the easier positions to scheme against, which is an issue Miami has faced the past two years with Suh.

The second personnel source pointed out Miami’s questionable roster decisions last year that caught up to the defense. The Dolphins let 2015 sack leader Olivier Vernon walk in free agency and tried to replace Vernon with defensive end Mario Williams, who flopped and had a career-low 1.5 sacks. The source also pointed out the loss of four-time Pro Bowl cornerback Brent Grimes as a move that hurt the team, as well as the season-ending shoulder injury to safety Reshad Jones after just six games. Miami’s linebacker play also was among the worst in the NFL, and the team is expected to replace two starters this offseason.

It is also worth noting that Suh will have his third defensive coordinator in three seasons with the Dolphins. In 2015, former defensive coordinator Kevin Coyle deemed Suh “The Chief” because Suh was his best player. But Coyle’s system failed early, and he was fired along with head coach Joe Philbin, in the middle of the season.

Last year, Vance Joseph came on board as defensive coordinator and changed how Miami played defense. He put Suh in the “Wide-9” scheme, which is similar to what Suh had played with the Detroit Lions. Suh also moved around to become less predictable. He played both defensive tackle spots and lined up some at defensive end during the course of a game.

The results led to Suh having an even better second season and he earned his fifth Pro Bowl selection after recording 72 tackles and five sacks. His best game was against the eventual Super Bowl champion New England Patriots in Week 2, when he recorded a career-high 12 tackles. Suh also had the game-saving tackle against San Francisco 49ers quarterback Colin Kaepernick in Week 12 during Miami’s run to the playoffs and 10-win season.

But the defense struggled overall and too often couldn’t get off the field. Joseph was hired by the Denver Broncos this offseason to become their head coach, leading Miami to promote linebackers coach Matt Burke to run the defense in 2017. Burke is planning to keep many of the schemes and philosophies Joseph implemented last season.

Miami is spending much of its offseason trying to find better pieces on defense to complement Suh. But if Suh has proved anything over the past two seasons, he will be a consistent and durable performer. It is up to the rest of Miami’s defense to raise its level of play around him.