With many teams in the thick of their fantasy football playoffs, the stakes are the highest they've been all season across fantasy football leagues. This weekend's games could make or break seasons, so it's crucial that fantasy managers make the right decisions. Picking starting and flex running backs is among one of those most important weekly decisions. Backs like James Cook and Christian McCaffrey helped win games for their teams last week while others like Breece Hall put up duds. So which running backs are the best starts this week? Let's take a look at the best backs to sit and start in Week 16.

Fantasy Football RB: Start ‘Em

Raheem Mostert

Mostert is the NFL leader in rushing touchdowns, with 18 on the year. He's already pretty much a must-start thanks to his high scoring, but that ramps up as he faces the Dallas Cowboys this week. The Cowboys just gave up a huge rushing game to Bills running back James Cook, who rolled for 36.1 PPR points while putting up 221 total scrimmage yards and two touchdowns. With Tyreek Hill's status uncertain for the game, look for Miami to get their ground game going, like the Bills did to annihilate the Cowboys.

James Cook

Speaking of James Cook, start him again this week the Los Angeles Chargers. Cook had the best game of his career against the Cowboys, and it paid off for his fantasy manages. This game isn't an outlier either, Cook has become more involved in the offense since Joe Brady took over as Buffalo's offensive coordinator. He's put up at least 100 scrimmage yards in each of the last five games. Cook's next game against the Chargers should continue this streak. The Chargers look defeated as a team, which should favor the Bills and Cook on Saturday.

Rachaad White

White has been a big factor in the Tampa Bay Buccaneers three-game winning streak. He provides much-needed balance to the Tampa offense and has become one of their offense's most valuable players. White has put up at least 80 yards in each of the last four games, scoring touchdowns in three out of four of those games.

Jahmyr Gibbs

For Jahmyr Gibbs fantasy managers, the patience paid off. Early in the year, many wondered why Gibbs wasn't getting more touches after the Lions invested a first-round pick for him. Now, he's seeing those opportunities and making the most of them. Against the Broncos, Gibbs had his second 100-yard rushing game of the season, accumulating 100 yards and a touchdown on 11 carries. He's become more consistent as the year has gone on, and his playmaking adds another weapon for the Lions.

Fantasy Football RB: Sit ‘Em

Javonte Williams

Javonte Williams became more productive toward the middle of the year for the Broncos, but is overall too inconsistent to count on. He had just 27 yards rushing against the Lions while averaging a measly 2.2 yards per carry. Williams hasn't averaged at least four yards per carry in a game since October and only has one rushing touchdown on the year. He has a bad matchup this week versus the New England Patriots, who have the No. 2 ranked run defense. All signs point to sitting Williams.

Jerome Ford

The Browns backup running back peaked back in November when he rushed for 107 yards in a huge win over the Ravens. However, Ford has yet to match that level of production. He had just 20 yards against the Bears last week and only has three rushing touchdowns on the year. With this week's game against the sixth-ranked Houston Texans run defense, Ford is too risky to start with fantasy football playoff games on the line.

James Conner

James Conner is coming off a couple strong games versus the San Francisco 49ers and Pittsburgh Steelers. He has 86 rushing yards and a touchdown against the 49ers after 105 rushing yards and two rushing touchdowns against the Steelers. Still, fantasy managers need to proceed with caution when starting Conner. Arizona is going up against the Bears this week, who have the NFL's top ranked run defense. Unfortunately for Conner fantasy managers, this is not a good matchup.