The Dolphins know without an improvement on third-down conversions, they will struggle to win games.

David Butler II USA TODAY Sports

DAVIE, Fla. (AP) -- The Miami Dolphins are third-rate on third down and getting worse, which they're eager to change beginning Sunday at Buffalo.

Miami ranks last in the AFC in third-down conversion at 27 percent, and in the past four games the Dolphins are at 20 percent (8 for 41).

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"If you don't convert third downs, you're going to have a tough time winning," quarterback Ryan Tannehill said Wednesday. "It's something we're aware of, and we're fighting to get better."

Poor play on third down is perhaps the biggest reason Miami's offense has scored more points than only four other teams.

The Dolphins (3-4) went 2 for 11 on third down in last week's 36-7 loss at New England. In their past two defeats, the Dolphins are 2 for 23 on third down.

They went 4 for 13 on third down when they were beaten at home by Buffalo 41-14 in Week 3.

"It has definitely been an issue," receiver Rishard Matthews said. "We've got to get it together."

Interim coach Dan Campbell said substandard production on first and second down is a big part of the problem.

"I don't care who you are, if you get into third and 10-plus, that's hard," Campbell said. "We have to get more production on first and second down. We can't have tackles for losses or no-gains or incomplete passes. Those are things we have to get out of."

Actually, the Dolphins have been pretty good on first down, when their average of 6 yards per play ranks seventh-best in the NFL. They're faced third-and-6 or longer 47 times, which is the league average.

But they're only 5 for 9 on third and 1, and 4 for 17 on third and medium (6 to 9 yards), ranking near the bottom in both categories.

"Maybe it's us rushing and not getting it -- I've dropped a couple of passes -- or Ryan not getting enough time," Matthews said. "Collectively we've got to get it together."

Third down has been Tannehill's worst down since he became a starter as a rookie in 2012. He has a career passer rating of 73.9 on third down, compared with 84.4 overall.

Part of the problem is Miami's perennially shaky pass protection, which defenses eagerly exploit on third and long, putting lots of pressure on Tannehill.

His third-down success rate has been woeful in the past four games, even though Miami won two of them. Over that stretch he has converted third down on only 6 of 33 pass plays (18 percent), while averaging a dinky 4.4 yards per attempt.

Buffalo ranks in the middle of the pack in third-down defense at 38 percent.

"We haven't been very good," coach Rex Ryan said. "That's certainly an area we want to get better at, and I know the Dolphins want to get better at as well. So something's got to give."