WHEN THE PATRIOTS RUN

This could be a career day for whomever gets the bulk of the carries Sunday. San Francisco's run defense has been historically bad, having already allowed more consecutive 100-yard rushers this season than any team in NFL history. Most of the backs who've cracked the century mark against the 49ers have also enjoyed career-high performances, among them Carolina's Fozzy Whittaker, Seattle's Christine Michael and Tampa Bay's Jacquizz Rodgers, none of whom have been particularly effective this year. With LeGarrette Blount doing most of the dirty work and Dion Lewis back in the mix with his elusiveness on full display, the Patriots should have no issues moving the ball on the ground against this porous defense. Advantage: Patriots

WHEN THE 49ERS RUN

The 49ers rank among the top five teams in the league in rushing yards per game, but numbers are somewhat deceiving. Former second-round draft pick Carlos Hyde has been one of the team's few bright spots with six rushing touchdowns but injuries have slowed his progress of late, paving the way for journeyman DuJuan Harris, who has emerged as a solid dual threat. The 49ers also benefit from having had two mobile quarterbacks this year in Blaine Gabbert and his replacement Colin Kaepernick. The Patriots have been good, not great, against the run this year and are still transitioning defensively following the trade of Jamie Collins. With Hyde, Harris and Kaepernick, San Francisco might have some luck on the ground. Advantage: 49ers

WHEN THE PATRIOTS PASS

While the run defense gets most of the blame for San Francisco's horrid performance, the secondary hasn't done much to stop the bleeding, particularly in the turnover department. The 49ers are somewhere in the middle of the pack in terms of interception rate, and most of their picks have come from linebackers. Only a small handful of teams have allowed more passing touchdowns than San Francisco, putting more pressure on cornerbacks Jimmie Ward, Tramaine Brock and rookie Rashard Robinson to be better ball hawks. The strength of New England's offense is its passing game, led by MVP candidate Tom Brady. With an abundance of weapons at Brady's disposal, it's hard to imagine his red-hot start hitting a roadblock against a defense that doesn't force turnovers or keep teams out of the end zone, even if tight end Rob Gronkowski (chest) is unavailable.Advantage: Patriots

WHEN THE 49ERS PASS

The 49ers are terrible in a number of areas, and their passing game deserves some of the blame. Head coach Chip Kelly's plan to implement his up-tempo offense in his first year at the helm has failed due to the team's lack of weapons. Even the quarterback switch from Gabbert to Kaepernick hasn't made enough of an impact, despite Kaepernick occasionally resembling the quarterback who brought this franchise to the Super Bowl in 2012. Jeremy Kerley could have some success in the slot, where the Patriots have struggled to find a consistent defender, but safety Patrick Chung will neutralize tight end Vance McDonald, who has become a legit scoring threat in recent weeks. With little else to work with as Torrey Smith nurses a shoulder injury, this will be a long afternoon for Kaepernick, even with New England's struggles in the secondary. Advantage: Patriots

SPECIAL TEAMS

One of the few bright spots in recent weeks for San Francisco is the sudden emergence of cornerback JaCorey Shepherd as a legit threat in the kickoff return game. The oft-injured Shepherd recorded three returns of 30 yards or more in his first crack at the job against New Orleans and figures to be San Francisco's primary returner down the stretch. This is the one area where the 49ers can gain an edge, which is particularly important with an offense that has trouble sustaining long drives. The good news for New England is the team appears to have cleaned up some of its coverage sloppiness, and kicker Stephen Gostkowski is back on track after a troubling stretch. The 49ers don't have many spots where they can get a leg up on New England, but a key return by Shepherd could be a game changer at any point. Advantage: 49ers

OTHER FACTORS

The Patriots travel west three times this year, but the trips are spread out over the course of the season, so fatigue hasn't been, nor should it be, a factor, even with this excursion covering more than 3,000 miles. The fact that they're playing one of the worst teams in the league negates any other factor that could work against them. The 49ers have been historically bad on both sides of the ball, especially on defense, while the Patriots are the odds-on favorite to represent the AFC in Super Bowl LI. There's always a possibility of a letdown in a game of such seemingly limited importance, but the Patriots should be wary of such hiccups after suffering a similar fate last year against the Eagles, Jets and Dolphins. There's just too much distance between these two teams, literally and figuratively, for this game to be competitive. Advantage: Patriots