Week 13 Fantasy Rankings: 4 Players You Just Can't Keep out of Your Lineup

Whether a player is having a down year, has no help around him, or has a team that's been struck by injuries, there are some players you just can't sit in fantasy football.

Obviously, each of them are some of the best at their position, because, had they not been in the picture, their teams would be even worse.

So, here are four fantasy football players you just can't keep out of your lineup.

Philip Rivers: QB, Chargers (at Jaguars)

Okay, so we know that Chargers QB Philip Rivers is in the midst of his worst season since becoming a full-time starter.

What's scary about this performance, however, is that Rivers is still putting up better numbers than most other NFL QBs.

But because of how well we saw him play from 2006-2010, he's held to a much higher standard, and rightfully so.

That being said, Rivers has thrown for over 3,200 yards, has a QB rating of 80.8, and a 61.1 completion percentage through 11 games.

If these numbers were being put up by a less-established QB, that would be impressive. If it's Philip Rivers, it's considered a down year.

Nonetheless, Rivers must remain a fantasy starting QB despite playing the No. 4 ranked pass defense this week in Jacksonville. San Diego is desperate for a win, so you can bet on Rivers slicing them for solid yards.

And, regardless of the outcome, he'll manage to throw a TD or two—but because he's in a down year, at least one pick or fumble will occur as well.

Either way, based on what he's done and what he's capable of, you cannot sit Philip Rivers.

Larry Fitzgerald: WR, Cardinals (vs Cowboys)

People should have sympathy for Arizona Cardinals WR Larry Fitzgerald.

He's been arguably the NFL's best receiver since being drafted in 2003, but, other than a few years with Kurt Warner under center, he's never had a stud QB.

And yet, Larry continues to play at a high level, and puts up solid numbers by making a mediocre QB look better than he's perceived.

So far this season, he's caught 51 balls for 888 yards and scored six times.

He may not be on pace to get 100 catches, but he'll surpass his yardage and TD total from 2010.

This week against Dallas, he'll be targeted quite often. The Cowboys have a good rush defense and pass rush, so to keep them honest, Fitz's production is crucial.

That said, the production will mainly be to outrun and outjump anyone in blue and silver who's covering him.

The weakness on Dallas is their pass defense, and they have no one who can match Larry one-on-one or even in double coverage. As long as he's given the opportunity to utilize his athleticism, Arizona will move the ball.

As for fantasy, well, he may not get too many receptions, but his yards will be solid and a TD or two is quite possible.

Eli Manning: QB, Giants (vs Packers)

Although most won't believe it until they see it, Giants QB Eli Manning is quietly having his best year as a pro.

So far, he's compiled 3,358 passing yards, 20 TDs, and a completion percentage of 62.9.

He's less than 700 yards shy of surpassing his single season best, and is just 11 TDs shy of his career best for touchdowns.

In Week 13, Eli and the Giants host the undefeated Packers, who have a vulnerable pass defense, despite leading the league with 22 INTs.

To that end, Manning will be significantly relied on, as New York has a weak rushing attack and their defense won't stop Green Bay.

Now, asking Eli to keep pace and match Aaron Rodgers is a lot, but his production is the Giants' offense. New York ranks No. 4 in passing but dead last in rushing. The Big Apple moves as his right arm throws.

And based on what he's already accomplished this season, along with a susceptible defense coming in, Eli will play well this week ,even if he can't be as quick and nimble as Rodgers.

He may not appear to be a gunslinger, but he's definitely a lot better than he's given credit for.

Matt Forte: RB, Bears (vs Chiefs)

For a QB or WR to be the lone offensive weapon on a team is one thing, because a QB has the luxury to dish the ball around, scramble if needed, and can get passing yards off a three-step drop with no pass protection.

A wide receiver may also have to make defenders miss, but not usually until they're downfield.

The RB ends up left with a wall of defenders to dodge along with a couple of designed blocks.

That's basically been the case for Chicago's Matt Forte all season.

He not only is the Bears offense when they're healthy, but he's expected to do even more now that there's been some injuries. But Forte has been producing like crazy. Through 11 games this year, he's compiled 1475 total yards (985 rush, 490 receiving) on 250 total touches.

Chicago has no passing game, and the defense ranks No. 30 against the pass.

So for the Bears to win, not only does Forte need to produce yards, but he has to avoid turnovers, must pass-protect, and has to control the game tempo all by himself.

It helps that his O-line is solid, and the WRs are good at stock-blocking, and don't forget Devin Hester on special teams.

But Chicago doesn't move the ball unless Forte moves the ball. This week against the Chiefs, expect more of the same.

K.C. does have a respectable pass rush and rush offense, but as long as Forte keeps surging ahead with the entire Mike Martz playbook on his shoulders, the Bears will win, and you'll get some great fantasy points.

Follow John Rozum on Twitter @ Sportswriter27