The key to success in fantasy football is drafting players who will exceed expectations and avoiding those destined to underachieve. For example, going into last year, few prognosticators thought much of Philadelphia Eagles QB Nick Foles, but owners who grabbed Foles were rewarded.

Ranked 35th among QBs prior to the season, Foles outscored fantasy heavyweights Tom Brady and Aaron Rodgers and high-profile selections such as Robert Griffin III, Eli Manning, Jay Cutler and Sam Bradford. And whereas owners of Brady and Rodgers spent early-round picks for their QB1, Foles was available via the waiver wire in most leagues.

That’s value. And that’s what you’re hoping for when you pluck the elusive sleeper from the tall grass of “average,” says Yahoo! Fantasy Football Expert Brandon Funston.

You won’t get Foles from the waiver wire this year, but sleepers (and busts) await those who do their homework. Check out Funston’s recommendations below.

Undervalued 

Quarterbacks

Ryan Tannehill, Miami Dolphins: First-year offensive coordinator Bill Lazor, who was the QB coach in Philadelphia last year under Chip Kelly, likes to throw the ball in an up-tempo scheme. It’s a good system for Tannehill to have a breakout season, according to Funston, who says, “Miami is trying to be that team this year, emulating Philadelphia. Tannehill has some seasoning under his belt now and he’s got the system; he could be this year’s Nick Foles. I like [him] a lot as a guy who you could get late who may ascend into the top 12 or top 15 range and should be one of those surprise guys.”

The third-year quarterback threw for over 3,900 yards, 24 TDs and 17 interceptions in 2013.

Sam Bradford, St. Louis Rams: Funston calls Bradford a “deeper sleeper,” but he says the former No. 1 overall pick’s fantasy value depends on whether he can stay on the field.

Bradford played in only seven games last year, throwing for three touchdowns three times. A knee injury ended his season early, but Bradford had nearly 1,700 yards, 14 TDs and 4 interceptions. His QB rating of 90.9 indicates what could be possible if he stays healthy.

“When he was healthy last year, he was actually playing pretty well,” Funston says. “Bradford is a guy I think many people are overlooking. As a fantasy back-up, I think there’s some upside there.”

Running Backs 

Terrance West, Cleveland Browns. The 5-foot-10, 225-pound rookie from Towson has turned heads thus far in training camp, and many believe he has the talent to win the starting job over Ben Tate, who came over from Houston via free agency.

“I’d put my money on [West] over Ben Tate,” Funston says. “I just don’t have any trust that Tate can stay healthy.”

Toby Gerhart, Jacksonville Jaguars. Gerhart will be the man in Jacksonville, and he could see 20-25 touches per game.

Funston says, “He’s a guy who’s going outside of the top 20 running backs being drafted, and I think he could be a top-15 guy. He’s a little more athletic than people realize. He can catch the ball. He’s going to be out there for three downs, and there are not a lot of those running backs in the NFL anymore.”

Shane Vereen, New England Patriots. New England had one of the most productive backfields in fantasy over the past few years, and the fourth-year running back is expected to get the bulk of the carries this season.

Vereen has extra value in leagues that award points for receptions. “He’s super active in the passing game,” Funston says. “He can get 6 or 8 catches on plenty of Sundays, but if he’s also going to get 15 to 20 carries thrown in there as well, there’s huge upside there.”

Wide Receivers 

Markus Wheaton, Pittsburgh Steelers. Funston calls the second-year pro out of Oregon State “probably my favorite value right now.”

Emmanuel Sanders and Jerricho Cotchery are gone, along with their combined 1,300-plus yards and 16 TDs. Funston says Wheaton will get plenty of opportunities, while opposing defenses concentrate on stopping Pittsburgh’s WR1, Antonio Brown.

Terrance Williams, Dallas Cowboys. The Cowboys’ woes on defense mean they will be playing from behind quite a bit and throwing the ball to catch up.

“Williams got his feet wet last year and looked good,” Funston says of the 6-foot-2, 210-pound former third-round pick. “He’s going to have a huge number 2 role opposite Dez Bryant, so he’s a guy I can see a lot of value in as well.”

Tight Ends 

Ladarius Green, San Diego Chargers. Green had 17 catches, 376 yards and 3 TDs last year as a backup to Antonio Gates. Gates isn’t getting any younger, and Funston says this could be the year the Chargers “flip the script” and go to Green, giving the 6-foot-6, 240-pound third-year man more opportunities.

“When they gave him a healthy amount of snaps last year, his athletic freakishness showed up and he had some big games,” Funston says.

Overvalued 

Quarterbacks 

Andy Dalton, Cincinnati Bengals. The Bengals lost pass-happy offensive coordinator Jay Gruden, who is now the head coach in Washington. In comes Hue Jackson, a run-oriented coach, and the change in philosophy could be enough to limit Dalton’s fantasy production.

“I don’t see Andy Dalton being a top 15 guy this year, where he was a top 5 guy last year,” Funston says.

Philip Rivers, San Diego Chargers. “[The Chargers] were really starting to become run-heavy last year, and to me that kind of points to them stacking up that backfield [with RBs Donald Brown, Danny Woodhead and Ryan Matthews] to be a run-heavy system,” Funston says.

Johnny Manziel, Cleveland Browns. “Johnny Football” is battling with veteran Brian Hoyer for the starting job in Cleveland. Even if the highly publicized rookie gets the gig, Funston expects him to struggle as a pocket passer in the NFL.

Because he’s a big name, Manziel could be overvalued by many fantasy owners.

Running Backs

Frank Gore, San Francisco 49ers. The Niners drafted Ohio State’s Carlos Hyde in May, and the bruising back could cut into Gore’s carries.

“San Francisco is ready to start sharing the workload a little bit more,” Funston says. In addition to Hyde, the 49ers also have Marcus Lattimore, a highly touted running back who missed all of last year with a knee injury.

Doug Martin, Tampa Bay Buccaneers. Martin, drafted in 2012, was a monster in his rookie season (1,454 yards, 11 TDs, 4.6 yards per carry), but he suffered a shoulder injury last year and missed half the season.

Even without the injury, Martin looked to be heading for a sophomore slump. In seven games, he ran for only 456 yards (3.6 yards per carry) and scored only one rushing TD.

“They’re talking about [head coach] Lovie Smith running a committee there, and they drafted Charles Sims, who’s basically a great receiving running back, so you get the feeling that maybe Martin’s going to at least be out on passing downs,” Funston says. “He’s a guy I’d steer clear of if you have to pay a high price to get him.”

Wide Receivers

Wes Welker, Denver Broncos. “He came out hot last year, but he only scored two touchdowns after Week 6,” Funston says.

Injuries, namely concussions, are another reason why Funston warns fantasy owners to be wary of Welker. “He’s too big of a risk, given where he’s being drafted in most leagues,” he says.

DeSean Jackson, Washington Redskins. Jackson thrived in the Philadelphia Eagles offense and had a career year last season. Fantasy owners chasing those numbers (1,300-plus yards, 9 TDs) could be disappointed in 2014.

“There’s a little bit of a less-lucrative passing game in Washington, and they also have Pierre Garcon, who led the league in targets last year,” Funston says.

Tight Ends 

Jordan Reed, Washington Redskins. Reed is a young player (drafted in the third round in 2013) who has good upside talent-wise but has struggled with concussions. He played in nine games last season and had 45 catches, 499 yards and 3 TDs.

“Guys who’ve had a lot of concussions and they’re young, that worries me a lot,” Funston says.

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