Tuesday Takeaways: Dolphins fall to 3–1

One week after conga-dancing through a 50-point win over the Broncos, the Dolphins were humbled Sunday by a Bills team wanting to prove it still has a hold on the AFC East.

• Both teams are now 3–1 and tied for first place in the division.

Why it matters: Miami, which lost 48–20, now faces serious questions about its defense — along with injury concerns on its offensive line.

What happened: Defensive coordinator Vic Fangio's defense let Buffalo quarterback Josh Allen finish with a perfect passer rating and four touchdowns.

• Fangio was questioned for leaving second-year cornerback Kader Kohou on wide receiver Stefon Diggs, who exploded for three touchdowns, despite All-Pro team captain Xavien Howard saying afterward he wanted the matchup for himself.
• Running back Raheem Mostert fumbled twice after fumbling just seven times in his career up to that point.
• Quarterback Tua Tagovailoa couldn't replicate his four-touchdown performance from a week ago, throwing for one score and one interception. He's now 0–4 at Buffalo's Highmark Stadium.

Between the lines: Starting center Connor Williams was out on Sunday, and Miami also lost Pro Bowl left tackle Terron Armstead to a knee injury in the second quarter.

• Armstead, a key contributor who missed Miami's first two games with a leg injury, has already been ruled out for Week 5.

What we're watching: Miami's next two games against the Giants and Panthers should be very winnable. Two wins would put the team at 5–1 heading into a tough Oct. 22 matchup against the Eagles.

What's next: The Fins return to Hard Rock Stadium to play the Giants at 1pm Sunday.