The calls for major changes within the Buffalo Bills organization have only gotten louder following another uninspired defeat in Week 16 to the Miami Dolphins. The Bills showed few signs of life in the 24-10 loss, which could serve as the final nail in the coffin for Chan Gailey’s coaching tenure.

Offense: D

The only reason this isn’t a straight F is C.J. Spiller. The RB was electric once again and Buffalo’s lone bright spot on offense, rushing for 138 yards on 22 carries. Spiller ripped off a 62-yard gain in the second quarter that was the highlight of the afternoon. Other than that, it wasn’t pretty on offense. The Bills had four turnovers -- fumbles from WR Stevie Johnson, TE Dorin Dickerson and QB Ryan Fitzpatrick, along with a late Fitzpatrick interception -- that played a major role in the loss. The Dolphins picked up 17 of their 24 points off turnovers. Had the game not ended two plays after Fitzpatrick’s interception, Miami would have probably scored after that one as well. Johnson had a rare bad game (four receptions for 44 yards, one fumble lost), but he can be forgiven considering his play this season. That’s not the case for the rest of the offense. It remains clear that Fitzpatrick isn't the answer at QB. Previous game’s grade: D

Defense: F

Buffalo’s defense continues to underwhelm and disappoint. The Bills were unable to stop Reggie Bush on the ground or in the passing game; Bush had 107 yards from scrimmage and three touchdowns. In particular, DT Marcell Dareus and Buffalo’s LBs -- Nick Barnett, Kelvin Sheppard and Nigel Bradham -- are all still struggling to bottle up the running game. Finding upgrades at LB must be a top priority for the Bills this offseason. DE Mario Williams was invisible (two tackles, no sacks). The read-option was a problem for the second week in a row. Had the Dolphins been more explosive on offense, this game could have been yet another blowout defeat. Previous game’s grade: F

Special teams: C-

There weren’t many plays of significance on special teams. It’s clear that the Bills miss Leodis McKelvin, who was responsible for several game-changing returns earlier this year. Jairus Byrd, Justin Rogers and Brad Smith did little to nothing in the return game. DT Alex Carrington did have his fourth blocked kick this season (three field goals, one extra point), but it didn’t amount to anything in the grand scheme of things. P Shawn Powell had a difficult day despite perfect weather (36.3 net average on four punts). Previous game’s grade: C+

Coaching: F

Is this the end of Gailey’s tenure in Buffalo? It should be. For most teams, this would be a simple answer. But the Bills have said all along that they would prefer to stick with Gailey because they can’t keep changing coaches every 3-4 years. Yes, that matters, but it also matters to have the right person in charge. The Bills are 15-32 under Gailey and only appear to be getting worse under his leadership. With Gailey’s job on the line, his team has turned in one lackadaisical effort after another. Publicly, players won’t ever say that he’s lost the team but the evidence on the field suggests otherwise. The Bills were flat throughout the entire game against Miami and struggled in all three phases -- which has been the case far too many times this season. Previous game’s grade: D

For more updates on the Bills, follow correspondent Mark Ludwiczak on Twitter @CBSBills and @MarkLud12.