The Miami Dolphins' run defense is stuck in reverse Youth Jahlani Tavai Jersey , perhaps taking the season with it.Poor tackling, botched assignments and a manhandling up front doomed the Dolphins on Sunday, when the Detroit Lions ran for 248 yards to win 32-21.It was Detroit's biggest total in 21 years, and the second bad game in a row for the Dolphins' run defense. They allowed 164 yards rushing a week earlier but still somehow managed to beat the Chicago Bears in overtime."We have a lot of work to do," defensive end Cameron Wake said. "I'm not panicking yet."Lions rookie Kerryon Johnson rushed for 158 yards on 19 carries, including a 71-yard draw play where he was untouched until tackled. LeGarrette Blount added 50 yards on 10 carries, and both repeatedly broke tackles as the Lions averaged 7.1 per rush."Johnson, LeGarrette, they're big backs," Miami defensive tackle Akeem Spence said. "With those guys, you have to tackle in committee. One guy can't bring them down. You need two, three guys. That's on the defense. We just have to be better."With the loss, the Dolphins (4-3) fell out of first place in the AFC East. Linebacker Raekwon McMillan acknowledged they played on their heels."We fell back on our attack-type mentality," he said.That meant the front seven was dominated, with the line surge so tepid Miami had not one tackle for a loss.The issue extended beyond running plays. Matt Stafford had plenty of time to throw and went 18 for 22 for 217 yards and two scores, with just one sack."We couldn't stop them," Miami coach Adam Gase said. "That's just what it was. They were executing better than us, and we just didn't do enough to affect the quarterback. It didn't seem like he got out of rhythm."That was really the No.