Since Jeff Ireland arrived as general manager in 2008, the Dolphins have spent more money and used more picks in the first four rounds of the NFL Draft on the offensive line than any other position.

Some of those decisions have paid dividends, including drafting emerging center Mike Pouncey, but the harsh reality is this:

Five years later, the Dolphins are still left with a unit that can’t consistently dislodge defenders in the run game, has too many breakdowns in pass protection and can’t dominate an opposing defense for more than short occasional stretches.

“The offensive line just hasn’t played as well” as it needs to, ESPN’s Ron Jaworski said off air this week. “Jake Long, I know he has nursed some injuries, but these are All-Pro players. There has been inconsistency on the offensive line.”

For some perspective on how much money and resources have been devoted to the line, consider:

During Ireland’s five-year tenure as GM (Bill Parcells was in charge until September 2010), not only did Miami use its first draft pick — and the No. 1 overall choice in 2008 — on left tackle Long and commit $58 million to him, but the first players Miami signed in free agency were offensive linemen in three of those five offseasons: Justin Smiley ($25 million in 2008); Joe Berger (less than $3 million) and then Jake Grove ($29.5 million) both in 2009; and Artis Hicks ($1.3 million) in 2012.

Richie Incognito, the starter at left guard, is in the second year of a three-year, $8.4 million deal.

Smiley, Grove, Berger and Hicks never made it to the end of their contracts. Neither did Vernon Carey, who was signed to a six-year, $42 million extension in 2009, but was ordered to shave the last two years off his deal as part of a 2011 pay cut. Other free agents came and went, including Pat McQuistan and Ray Willis.

Hits and misses

Then there’s the draft. Besides taking Long first, the Dolphins also invested draft picks on Shawn Murphy (a fourth-round washout), sixth-rounder Donald Thomas (who has started five games for the Patriots this season), sixth-rounder Andrew Gardner (never panned out), 2010 third-rounder John Jerry (starting at right guard), Pouncey (picked 15th in 2011 and now blossoming), and 2012 second-round pick Jonathan Martin (starting at right tackle).

The current group of starters — Long, Incognito, Pouncey, Jerry and Martin — has played well at times but not as efficiently or consistently as the Dolphins expect. The Dolphins rank only 28th in rushing yards per attempt (3.6), and coach Joe Philbin attributes that primarily to substandard blocking, with receivers, backs and tight ends also sharing the blame.

“We’ve got to get our run game back on track, do a better job sustaining blocks and moving people,” Long said.

Said Incognito: “We have to create more space. We should be able to run against any [defensive alginment]. It’s frustrating because we know what type of running game we can be.”

Grading out

According to Pro Football Focus (PFF), the Dolphins have had their most success running directly behind Incognito (5.1 yards per carry) and Pouncey (4.5 to his left, 4.3 to his right). Conversely, the Dolphins are averaging 3.3 yards per rush behind Jerry, 2.7 behind Martin and 2.2 to the right edge on Martin’s side.

As for Long, the news is mixed, according to PFF. Runs to the edge on the left side — with Long blocking — are averaging a robust 4.8 yards, but runs directly behind him are averaging 2.9.

PFF, which analyzes every play of every game, ranks Long 47th overall among 72 qualifying tackles, down from second in 2009 and 2010 and 21st last year. Though he has battled injuries in 2010 and 2011, he said he feels healthy and believes he is playing well. “I’m my biggest critic,” he said.

PFF ranks Martin 66th among 72 tackles. He has allowed four sacks and 28 quarterback hurries, among the highest totals among tackles. “I’ve played well at times, bad at times,” he said.

Among 78 qualifying guards, PFF ranks Jerry 53rd and Incognito 56th, with Jerry listed as allowing two sacks and Incognito three.

Jerry “has good size, good athleticism,” Philbin said. “He has not been on the ground as much as early on. He has a chance to be a good player.”

Pouncey has been the unit’s most consistent starter. PFF ranks him third among centers, behind only Minnesota’s John Sullivan and Washington’s Will Montgomery. Pouncey hasn’t allowed a sack and permitted just one quarterback hurry.

Excluding Pouncey, pass protection has been shaky at times. The Dolphins rank 17th in sacks allowed per pass play, with 27 permitted in 10 games. Long and Martin have been responsible for four apiece.