ORCHARD PARK, N.Y. -- “Execute” was a popular word at the Buffalo Bills' practice facility this week.

Players and coaches pointed to a lack of execution when describing what has ailed the 7-5 Bills, who came into the season with Super Bowl expectations. They’ve now lost four of their last seven and have lost ground in the playoff hunt. So, why aren’t things working? Where’s the magic from last year’s passing offense? Why the inability to stack wins?

“This year I feel like we haven’t played our best ball for whatever reason,” wide receiver Stefon Diggs said. “We can find a million reasons why, but it all comes down to execution. ... We have damn near the same team, for the most part. As players, you want to dive in deeper, figure out what’s the problem ... for us, finding that why.”

If the season ended today, the Bills would get the final spot in the AFC playoff field. They have five games left in the regular season and some of the tests to come aren't easy, starting with a matchup against a familiar quarterback in Tom Brady when the team heads to Tampa on Sunday (4:25 p.m. ET, CBS). The Bills' No. 1-ranked passing defense (165.3 pass yards per game and eight passing touchdowns allowed) will go up against the league's top passing offense (311.1 pass yards per game and 34 passing scores).

“I love playing against Tom Brady,” defensive tackle Harrison Phillips said. “I really do. I think that it's incredible to have a chance to go against somebody who's that amazing of a football player and the things that he's done in his career.”

Brady has a 32-3 record against the Bills, the best win percentage by a quarterback against a single team since 1950, as well as the most wins any quarterback has had against a single team, per ESPN Stats & Info.

The biggest problem for the Bills is that over the last eight games the team has been the model of inconsistency, blowing out weaker opponents but struggling to finish other games, going 0-4 in games decided by one score.

“Throughout the game, we move the ball with no problem. It's just like when we get in that red zone, we get in that fringe area ... it gets a little tighter,” Diggs said.

In its four wins over the last eight games, Buffalo has averaged 35 points per game and has a +86 point differential. But in the four losses, the team has averaged just 15.5 points per game and has a -36 point differential.

This is a team that hasn’t been able to stack wins since the first two weeks of October.

"We definitely have to continue to make adjustments and improve some of the things that we're doing,” coach Sean McDermott said. “But the season’s still out there for us right now and we've got a big test, a big challenge this week going down to Tampa.”

The Bucs game is followed by a visit from the Carolina Panthers (5-7) in Week 15. The Bills will then travel to New England to again face the Patriots (9-4). The season ends with home games against the Atlanta Falcons (5-7) and New York Jets (3-9).

Three of their five remaining games are against the NFC South. The Bills have already played most of their conference games, including finishing 1-3 against the AFC South.

Hurting Buffalo as it attempts to claim the best possible spot in the playoffs is its 5-5 conference record, currently the second-worst percentage among the would-be playoff teams. (The Kansas City Chiefs are 3-4.) Winning the remaining AFC East matchups could make a big difference in playoff seeding.

The Bills also lost to the teams currently directly below them in the AFC playoff picture -- the Steelers and Colts -- which would lose Buffalo the head-to-head tiebreaker. Beyond that, the race is tight because 12 teams in the conference are .500 or better.

So while there’s still a solid amount of football to be played, the window is getting tighter. Winning the division remains a possibility (32.7% chance, per ESPN’s Football Power Index) and their odds of earning a playoff spot are high (84.9%), but if the Bills lose more games, particularly to AFC opponents, the path ahead could be tricky.

“We’re trying to make the corrections," safety Micah Hyde said. "We're trying to do stuff right, trying to fix our weaknesses and fix some of these runs. And until we do, or when we do, ... we’ve got to make things happen.”