After such a promising start, the Miami Dolphins are experiencing a harsh fall back to Earth. With a 24-16 loss to the Minnesota Vikings on Sunday, Miami has now lost three straight games and sits at .500 on the season. The AFC East race has become one of the toughest in the NFL, and the Dolphins may fall behind if they don't get back on track soon.

Many of the issues that plagued Miami in previous games stuck around on Sunday, namely injuries at quarterback. Skylar Thompson left the game in the second quarter due to a thumb injury, marking the third straight game a Dolphins' quarterback has suffered an injury. Teddy Bridgewater did all he could in relief, but it wasn't enough to beat the team that drafted him.

While there were some positives, Mike McDaniel and the coaching staff have plenty to address this week. With that said, let's lay out some key takeaways from the Dolphins' loss to the Vikings.

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3. The Dolphins need their cornerbacks

Miami isn't just dealing with injuries at quarterback, but also in the secondary. Depth cornerbacks such as Kader Kohou and Keion Crossen missed the Vikings game, but that's far from the main concern. That would be injuries to their top two corners, Byron Jones and Xavien Howard.

Jones has not played at all this season as he continues to rehab an Achilles injury. His recovery is reportedly going slower than expected, and he may not play at all this season. Considering he had 10 passes defended last season, he would be a major loss if he can't return this season.

Howard played on Sunday after missing the previous game with a groin injury, but he clearly wasn't at full strength. The seventh-year cornerback had just three tackles and a pass defended. He also looked out of sorts on some plays, including one where he misread the play and left Justin Jefferson wide open.

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The Dolphins have missed their best corners, as they have the 25th-ranked passing defense in the league. If they want to make the playoffs, the secondary has to improve, and that means getting healthy.

2. Tyreek Hill and Jaylen Waddle are the NFL's best WR duo

Both Hill and Waddle have been lighting it up in their first season together in Miami. Hill leads the entire league with 701 receiving yards, while Waddle is fifth with 533 yards. The Dolphins made a big splash by acquiring Hill to form the NFL's fastest wideout duo, and it has paid off so far.

The dynamic duo had another great day against the Vikings. Hill had 12 catches for 177 yards, while Waddle had six catches for 129 yards. While Mike Gesicki may have had the touchdowns, Hill and Waddle were the main sources of offense.

What makes this performance so special is who was under center for Miami. It's one thing to play well with a starting quarterback in, but to keep it up with a backup is even more impressive. If Hill and Waddle can keep playing like this, few defenses will be able to stop them.

1. The Dolphins need Tua back

It's no coincidence that Miami's current skid started when Tua Tagovailoa suffered a scary concussion in Week 4 against the Cincinnati Bengals. The Dolphins have dropped three straight games since that moment, and they have looked significantly worse.

Tagovailoa may not be an MVP-level quarterback, but he is still Miami's best option and a leader on the team. His return will be a huge confidence boost for the Dolphins to find their groove again. He should return against the Pittsburgh Steelers on Sunday, and maybe Miami can get back in the win column along with it.