There were plenty of issues for the Patriots in their 33-21 loss to the Bills, but none were more impactful than the team's struggles on third and fourth down. It shouldn't be surprising that a key divisional battle came down to the two most critical downs in the game, but what was surprising was how ineffective the Pats were on both sides of the ball when it came down to the key moments.

"That was really the story of the game, their efficiency on third (6-of-12) and fourth (3-4) down, and we were 1-for-10 on third down," said Bill Belichick on Monday morning after assessing the film. "Obviously we have to do a better job in both areas."

"We should have skipped some fourth downs and third downs," lamented Mac Jones following the loss. "First and second downs we could have had bigger plays from me. I think like you're talking about, those are the plays you want to make and we did a good job making some of them. But we really don't even want to be in that spot. Every time it puts Josh [McDaniels] in a hard position and it puts a lot of the other players in a hard position, too."

Here's a closer look at how much of an impact fourth downs had on the outcome, with a sprinkling of third-down failures that might've been even more disappointing.

Buffalo sends an early message

4-2-NE 3 (6:43) (Shotgun) J.Allen pass short left to I.McKenzie for 3 yards, TOUCHDOWN.

After deferring the opening toss and forcing a Patriots three-and-out, the Bills marched down the field on their opening possession, converting the only third down they faced in between the 20's. That third-down conversion was a sign of things to come later in the contest, with Isaiah McKenzie outrunning Myles Bryant on a crosser and picking up the conversion. The Bills pushed all the way inside the Patriots' five-yard-line.

The Pats would get a goal-line stop on 3rd-and-2, but the Bills refused to settle for a field goal and set an early tone with their fourth-down attempt. With no pressure on quarterback Josh Allen, he calmly went through his reads before finding McKenzie in the back of the end zone for the 7-0 lead.

"We just felt like we had a good plan overall, I would just say that," said Bills coach Sean McDermott after the game of the fourth-down aggression. "Those aren't always easy decisions. I thought the offense did a great job of executing.

Pats grind out a counterattack

4-1-NE48 (3:36) D.Harris right tackle to BUF 48 for 4 yards (T.Edmunds).

4-1-BUF28 (15:00) D.Harris right end pushed ob at BUF 16 for 12 yards (A.Klein)

After Buffalo took the early lead, the Patriots countered with their own 13-play scoring drive, but their failure to convert a 3rd-and-1 (Harris stuffed) and 3rd-and-2 (Bolden stuffed) required an early commitment to aggressiveness. The Patriots would attempt and convert both fourth downs en route to getting on the board, with Damien Harris showing why he was one of the few bright spots from the game, picking up both first downs.

"This was an important game," said Harris after the game of going for it on fourth down. "We weren't going to hold anything back. The coaches made the decisions that they made. As players, it's our job to go out there and execute."

Goal-line stand provides a bright spot

4-1-NE1 (4:51) (Shotgun) J.Allen pass incomplete short right to E.Sanders

The defense made a couple of plays during the second quarter, holding the Bills to a field goal on their second possession of the game by getting a stop on the only third down they forced Buffalo into on the drive. But Mac Jones' interception on the ensuing drive threw the defense right back into the fire at their own 33-yard-line, down 10-7.

Four plays later Buffalo was knocking on the door from the Patriots' one-yard-line, but three incompletions later New England had an energizing goal-line stand, with Allen failing to connect with Emmanuel Sanders on fourth down.

For a brief moment, the Patriots looked like they were turning a corner, but after another quick three-and-out by the offense, Buffalo took back over at the New England 42-yard-line.

Buffalo extends their lead

4-7-NE34(2:15) (Shotgun) PENALTY on NE-C.Barmore, Encroachment, 5 yards, enforced at NE 39 - No Play.

4-2-NE 39(2:15) (Shotgun) J.Allen pass short middle to S.Diggs to NE 11 for 23 yards (D.McCourty; J.Collins).

With the Bills again threatening deep inside New England's territory, the Patriots defense got off to a good start after the interception, with an incompletion, a two-yard run and then a one-yard run on 3rd-and-8. Buffalo lined up on 4th-and-7, despite being in field goal range and got Christian Barmore to jump offsides, giving the Bills an easy five yards and shortening the fourth-down distance to just two yards.

Allen would connect with Diggs for the conversion, with no pass rush pressure from the Patriots as Allen had time to squeeze a tight pass to his favorite receiver. Still, the Pats would win the ensuing first and second down, setting up another key 3rd-and-11.

The Patriots rushed just three players, leaving Jamie Collins as a spy for Allen, but even with seven in coverage, the Bills quarterback was still able to find Diggs again, this time up the seam in between three different Patriots. That made the score 17-7 just before the half.

Patriots grind out a response, again

4-1-BUF23 (5:26) M.Onwenu reported in as eligible. M.Jones up the middle to BUF 17 for 6 yards (T.Edmunds; C.Basham).

4-3-BUF10 (3:02) (Shotgun) M.Jones pass short middle to J.Meyers to BUF 3 for 7 yards (M.Milano).

After scoring a touchdown late in the first half, the Bills got the ball to start the second half and again went right down the field on the Patriots defense. They'd convert a 3rd-and-10 along the way, with the Patriots sending five rushers but Allen avoiding the rush and making a throw back into the middle of the field that somehow found Emmanuel Sanders.

On their next set of downs, the Bills took two penalties that they were unable to overcome, failing to convert a 3rd-and-14 and settling for a field goal to make it 20-7.

With the game slipping away, the Patriots needed an epic drive and got it, but once again, it was a grind. They'd convert a 3rd-and-8 early on, but would be stopped short on two later third downs that forced two more fourth-down attempts, both converted. The first, a Mac Jones sneak, and the second a rollout with Jones going back into the teeth of the defense, throwing on the run to Jakobi Meyers for the first down. They'd make it 20-14 with a touchdown two plays later.

The Pats offense had one of their worst third-down games of the season, but still found a way to make some plays in the big spots on fourth down to keep the game from getting out of reach.

Defense can't get last stop

4-1-NE34 (4:27) J.Allen left end to NE 26 for 8 yards (D.McCourty)

Despite the full-game struggles in all phases, the Patriots continued to hang in there, as if waiting for the clutch plays they made during their seven-game win streak to suddenly kick in.

After they closed the score to 20-14, the Bills didn't blink, putting together their most efficient scoring drive yet, needing to convert just one 3rd-and-2 during the nine-play, 66-yard touchdown drive that made it a two-score game again at 26-14 with a missed two-point conversion.

In response, the Patriots didn't blink either, putting together their best drive of the game, going 10 plays, 75 yards and once against briefly making it a one-score game at 26-21. The Pats offense didn't face a third or fourth down on the drive, though it took over seven minutes off the clock when time was becoming precious.

The Bills got the ball back with 7:37 left in the game, and despite not forcing a punt the entire game, the Patriots defense needed just one single stop or takeaway to give their offense a chance to win the game.

The D got off to a good start, immediately putting the Bills in a 3rd-and-10, but once again Buffalo didn't blink, with Allen again finding McKenzie on a long crosser with Myles Bryant in pursuit.

"What hurt us were some of the over routes against man and zone," said Belichick on Monday of McKenzie's key catches. "We obviously didn't do a good enough job of rushing or those plays take a while, so between the pass rush and the coverage, it's just not good enough and great execution on their end."

But that wasn't the last chance, as a third-down stop set up a key 4th-and-1 with 4:17 left. This time Allen rolled out evading both Jamie Collins and J.C. Jackson behind the line of scrimmage to pick up the first down.

Even that wasn't the last chance, as the Bills would land in a 3rd-and-10 one more time. Allen would use a shovel pass to pick up 19 yards to Diggs, as the Bills would punch in one more touchdown to put an exclamation point on their impressive victory.

"To be able to have that trust means a lot," said Josh Allen after the game of the fourth downs. "Again, when you convert those and continue to convert those, what a killer it is for a defense. That's a really good team we just played. Obviously, they've had a lot of success this year. It's an elite defense. Again, having that trust to go for it on fourth down situations, that's big for us. It gives us some groove. It gives us some confidence going forward. I can't thank Coach enough for putting us in this position and believing in us."