We have a lot of pieces on numberFire geared toward helping you figure out which players you should roster in your DFS contests on FanDuel, but an important aspect of the DFS process is figuring out who you shouldn't play.

Narrowing down your list of potential plays by avoiding those who are destined to underwhelm can go a long way toward helping you create winning lineups.

Inevitably, some of the players I feature in this article will blow up and pop for a big game, but that comes with the territory of doing a piece like this one -- unless I'm going to tell you to avoid playing dudes who aren't on anyone's radar. I'm trying to avoid that. I want this piece to be useful.

Here are some players I'm fading on this Sunday's main slate.

Justin Herbert, QB, Chargers ($7,500)

Justin Herbert has a brutally tough matchup at the Denver Broncos, and we need to be concerned about the chances the Los Angeles Chargers sit their star quarterback for a portion of this game.

First, the matchup. Denver's D has been fantastic for most of this season. They're especially tough against the pass, ranking sixth-best by our schedule-adjusted metrics. They've permitted the fourth-fewest FanDuel points per game to quarterbacks (13.9).

Herbert had just 238 scoreless passing yards at home against Denver earlier this campaign. He's topped 278 passing yards in only one of five games versus the Broncos in his career.

On top of that, there's a chance that LA could sit Herbert for some -- or all -- of this game. The Bolts can improve their seed if the Baltimore Ravens lose, and coach Brandon Staley said the result of the Ravens' game will impact how they approach their own game. You'd have to assume Herbert would be the most likely candidate to sit if the Bolts go that route. And even if the Ravens lose, it wouldn't shock me if Herbert doesn't play the whole game.

All in all, Herbert just isn't worth the risk in my eyes.

Rhamondre Stevenson, RB, Patriots ($6,600)

There are times this season when Rhamondre Stevenson at this salary would've been a fantastic play. Week 18 is not one of those times.

For starters, the New England Patriots have a difficult road matchup at the Buffalo Bills. The Bills have kept the running back position to just 17.5 FanDuel points per game, the eighth-fewest. We rate them as the second-best run D.

The matchup wouldn't matter quite as much if Stevenson was getting workhorse volume, but he played only 57% of the snaps a week ago while Damien Harris handled a 48% snap rate. Stevenson's reduced role may be performance-based as he hasn't been very productive of late, getting held to 6.1 FanDuel points or fewer in three of his past four games.

A negative game script -- which is what the Pats are expected to face as a 7.0-point road 'dog -- would likely help Stevenson's outlook more than Harris', but Stevenson's declining role, shoddy recent fantasy production and bad matchup have me looking elsewhere at running back.

Michael Pittman, WR, Colts ($7,300)

The Indianapolis Colts have a tasty home matchup with the Houston Texans. It's a nice spot for their offense, but I'm not sure they'll be able to take advantage of it. If the Colts can, it'll like come on the ground.

Houston's D has been a run-funnel defense all year long. They've actually given up the fourth-fewest FanDuel points per game to wideouts (21.4) -- a result of their decent pass defense as well as opponents seeing a lot of positive game scripts.

The Colts' offense has been miserable this season, and with Sam Ehlinger starting under center in Week 18, that doesn't figure to change much.

Indy's bad quarterback play has crushed Michael Pittman Jr.'s fantasy production. He's averaging only 10.4 FanDuel points per game for the year (30th among receivers) despite ranking eighth in targets.

At a $7,300 salary, Pittman is a tough sell in Week 18.