Start 'Em, Sit 'Em Week 4: One Must-Sit Starter from Key Positions

Unfavorable matchups or injuries can be a major cause for concern for some starters in fantasy football this week.

Whether they are playing against a tough defense, battling an injury, or both, you must take caution before just signing up for another week with the same starting lineup.

Let's take a look at which starters are a must-sit in Week 4 along with a suggestion for a possible replacement for each of them that may be available on your waiver wire right now.

Note: Average weekly point totals are based on points from ESPN standard leagues.

Quarterback

Sit 'Em: Eli Manning, New York Giants

Average Weekly Point Total: 16.7

Manning's average weekly total is very misleading, considering that he dropped 34.8 points in Week 1 and has followed that up with 12.0 points and 3.4 points in Week 2 and Week 3, respectively. While he's thrown five touchdowns, his eight picks have been a nightmare for fantasy owners.

In Week 4, the mistake-prone Manning will be up against the Kansas City Chiefs. Not only do the Chiefs lead the AFC with nine total takeaways, but they also lead the NFL with 15 sacks. That's especially bad news for the Giants porous offensive line that allowed seven sacks last week against the Panthers. With little time to throw against a defense that specializes in forcing turnovers, it looks like a must-sit game for Manning and his fantasy owners.

Possible Replacement: Alex Smith, Kansas City Chiefs 

Availability: Owned in 41.6 percent of ESPN leagues

Smith has yet to commit a single turnover this season, and he has also thrown for 669 yards and four touchdowns in three games. Adding to his production, Smith has also ran for 114 yards on 23 attempts.

The G-Men have not been able to stop a nosebleed defensively—with a No. 17 ranking against the pass and No. 27 ranking against the run. Even if he doesn't start out great in this game, Smith will get plenty of chances to rack up yardage, as the Giants will likely continue to turn the ball over and give away extra possessions throughout the game.

Running Back

Sit 'Em: Reggie Bush, Detroit Lions

Average Weekly Point Total: 12.0

Bush's Week 1 tally of 191 total yards and one touchdown has owners yearning for a similar game in Week 4, but injury concerns should be one of the factors at the forefront when considering starting Bush.

The Lions back sat out Week 3 against the Washington Redskins with a knee injury. That followed a Week 2 performance in which Bush didn't produce much against the Arizona Cardinals—the game in which he injured his knee—with just 69 total yards and no scores.

Fellow back Joique Bell has been impressive in support of Bush. In Week 3 against the Redskins, Bell filled the void by totaling 132 yards and one touchdown in what has been a solid all-around season so far.

Bush's statistical concerns are compounded by the fact that, this week, he's up against the Chicago Bears and their turnover-forcing defense that leads the NFL with 11 takeaways (six fumbles) and sports the No. 8-ranked rush defense.

As reported by Michael Rothstein of ESPN.com, Bush is expected to play in Week 4, however, you should approach with caution.

Possible Replacement: Brandon Bolden, New England Patriots

Availability: Owned in 5.4 percent of ESPN leagues

If you're in a bigger league, the cupboard is bare as far as running backs are concerned. Bolden may be a bit of a risk, but he is available and proved he could be worth a look after a Week 3 showing in which he totaled 100 yards on just eight total touches, with a 46-yard run being the brightest spot.

Running backs Stevan Ridley (3.4 yards per carry) and LeGarrette Blount (3.6 yards per carry) have yet to show that kind of explosive play this season. Bolden is listed as questionable, per ESPN.com, but this was also the case for him going into last week.

As long as he's healthy, Bolden should get some touches after impressing last week. However keep an eye on that injury report.

Wide Receiver

Sit 'Em: Andre Johnson, Houston Texans

Average Weekly Point Total: 9.3

Johnson started off the season on fire with 12 catches for 146 yards in Week 1, but since then, he's seen his production steadily decline, with injuries being a major concern.

In Week 2, he left the game late in the fourth quarter with a concussion ,and last week, his day was ended even earlier because of a shin injury. As a result, he is listed as questionable and a potential game-time decision, per ESPN.com.

As if a leg injury isn't enough to be worried about for a wide receiver, even if he does play, Johnson will be facing off with the Seattle Seahawks and their No. 1-ranked pass defense this week. With Richard Sherman and Brandon Browner in the secondary, Seattle has two big, physical corners who can shut down any receiver in the NFL.

Possible Replacement: Kenbrell Thompkins, New England Patriots

Availability: Owned in 52 percent of ESPN leagues

Thompkins isn't putting up huge numbers by any stretch, with just nine catches for 130 yards in three games, but he did score two touchdowns last week. Also, his 28 targets are second on the team behind fellow receiver Julian Edelman.

Both Danny Amendola (doubtful, groin) and Rob Gronkowski (questionable, back) are uncertain for the Week 4 game against the Atlanta Falcons, per ESPN.com, so Thompkins should continue to see steady targets. On top of that, the Pats will be up against the Atlanta Falcons and their No. 25-ranked pass defense.