Miami Dolphins

Miami Dolphins sign defensive tackle Marvin Austin

If not for Ryan Tannehill’s flair for late-game dramatics, the Dolphins’ biggest story through the season’s first three weeks would be their shocking inability to stop the run.

Once considered impenetrable, the Dolphins’ high-priced front seven has surrendered 108.7 rushing yards per game, ranking in the bottom half of the league.

They have been particularly generous the past two weeks, allowing the Colts and Falcons to grind out 133 and 146 yards, respectively. On the season, the Dolphins have allowed 4.7 yards per carry, sixth-most in the league.

And the news on that front got no better Tuesday, as the Dolphins decided to place defensive lineman Vaughn Martin on injured reserve.

What exactly happened to Martin is a mystery. He wasn’t on the injury report at all last week and played 25 snaps on Sunday, his most action of the season.

The Dolphins are obligated only to release injury information if a player leaves the game, and Martin did not. So by inference, he either played through the issue Sunday or somehow got hurt Monday when the team was off.

Martin signed a two-year, $4 million contract with the Dolphins in the offseason.

To replace him, they have added free agent defensive tackle Marvin Austin, a talented but underachieving run-stopper who should bolster an ailing defensive front.

Austin, a former second-round pick of the Giants, tried out with the team last week, but the Dolphins waited until Tuesday to sign him.

Despite being taken with the 52nd overall pick in 2011, Austin appeared in just eight games in two seasons with the Giants, logging five tackles.

Austin sat out his last season at North Carolina while serving an NCAA suspension, and then tore his pectoral muscle as a rookie. Last year, he missed half the season with a back injury and needed knee surgery after the season ended.

The Giants decided to part ways with Austin last month.

“I don’t even want to think about it; I don’t even want to talk about it,’’ Austin said of his string of bad luck.

“I feel like this is a new beginning for myself,’’ he added. “I’m going to take full advantage and am grateful to be here.’’

Despite his struggles, Austin was a highly rated prospect out of college for a reason. The ability is there. When asked about his lack of productivity as a pro, Austin said the system in New York didn’t properly suit his skill set.

The Giants wanted him to play at around 315 pounds — and Austin believes that heaviness took away his athleticism. He’s now down to 307 and feels lighter on his feet.

Austin was emphatic that he could play against the Saints, if asked. The Dolphins probably will need him.

Defensive lineman Paul Soliai missed the Falcons game with a knee injury, and there’s no guarantee he will be back anytime soon, either.

Soliai said Tuesday that he’s “50-50’’ to play against the Saints next week but hasn’t yet been cleared to practice.

“I’m getting better every day,’’ Soliai said. “I’m excited, the more I’m walking. I just can’t wait to get back on the field, but it’s going to take time. I’m going to wait until I’m really healthy and get out there and play how I did before.’’

Soliai is part of a banged-up Dolphins front seven, which includes Cameron Wake (knee) and Koa Misi (shoulder). Wake’s status for Monday is unknown, but the prognosis is better for Misi. He is expected to be available for the Saints game, according to a league source.

All three were out for extended stretches of the Dolphins’ come-from-behind win over the Falcons. And they were missed. Tannehill’s late-game heroics masked the team’s defensive deficiencies; Atlanta averaged 4.9 yards per carry, often running through gaping holes.

During the Fox broadcast, analyst Tim Ryan pointed out how the defensive line often used stunts that backfired, with would-be tacklers running themselves out of the play.

“It’s got to get better, it’s got to get better,’’ said defensive coordinator Kevin Coyle. “It was one of those kind of games where it was a combination of things. We missed a lot of tackles in the ball game, that was not good.’’

Added defensive tackle Jared Odrick: “We know what we have to do to get better, and we’re going to do it this week.’’

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