Running back Christian McCaffrey is not buying into the negativity surrounding the San Francisco 49ers after two straight losses have dropped their record below .500.

“I think the vibe is probably a lot lower outside of this locker room than it is inside,” McCaffrey said this week about the 49ers. They are tied for last in the NFC West with the Los Angeles Rams, but are only one game behind first-place Seattle and Arizona.

“I think our team is hungry,” he continued. “We still have everything in front of us and we’re ready to go.”

How ready they are will be tested on Sunday night, when the 49ers head East for the third time in four weeks, this time facing the top team in the AFC East, the Buffalo Bills (9-2).

For a team that needs a strong late-season push to make the playoffs — and possibly even reach the Super Bowl again — San Francisco faces several challenges. The team is dealing with injuries to key players and the possibility of a lake-effect snowstorm, which could interfere with their game plan.

Quarterback Brock Purdy is expected to play after missing last week’s 38-10 loss to Green Bay due to a sore throwing shoulder. However, the 49ers have ruled out five starters, including star pass rusher Nick Bosa (hip, oblique) and left tackle Trent Williams (ankle).

The Buffalo area is under a lake-effect storm warning, with the forecast predicting 20 to 30 inches of snow over 12 to 16 hours starting Saturday.

“You’ve got to be ready for anything, just like you are with injuries,” said coach Kyle Shanahan. “But we fully understand what the elements may be.”

While the weather will be the same for both teams, the Bills are used to playing in snowy conditions. They’ve faced three major storms over the past two years. In January, the NFL had to delay Buffalo’s wild-card playoff win over Pittsburgh by one day due to the weather.

“If there’s anybody that’s done it enough, it’s me,” said Bills quarterback Josh Allen, who is from California but played college football at Wyoming. “I feel like I’m very comfortable with whatever weather elements are thrown our way.”

The Bills have had a strong season, with their best record through 11 games since 1992. They have won six straight games and scored 30 or more points in each of their last five games. They are also one win away from securing their fifth straight division title.

Coach Sean McDermott did not expect to be in a position to clinch the AFC East in Week 13. The Bills’ closest rival, Miami, lost to Green Bay on Thursday night, bringing their record to 5-7.

“I don’t think you think that far ahead, really,” McDermott said. “I’m certainly grateful for it. And I credit the players for the way that they’ve played.”

The Bills are coming off a bye week and are getting healthier. Linebacker Matt Milano, who has been out for 14 months with a broken leg and torn biceps, might return soon.

“Obviously, feeling confident about what we got going on here,” Allen said. “But we’re not into the playoffs yet, job’s not finished. And we’re just trying to find a way to go 1-0 this week.”