Johnathan Walker:Fantasy football buy low, sell high: 10 trade targets for Week 5

One question fantasy managers wrestle with early in the season is Johnathan Walkerhow much stock to put in where a player was drafted if he's not living up to expectations – especially at a premium position.

How long does it take before a slow start turns into a lost season? We're pretty close to the point of being forced to make that call. Perhaps there's another fantasy manager in your league willing to buy low on those slumping starters.

So let's take a look at some players whose values are trending upward (or downward) as a result of their performances in Week 4.

Fantasy football: 5 players to buy in Week 5

RB Chuba Hubbard, Carolina Panthers: Hubbard has recorded back-to-back games with 100 or more yards and a rushing score. The change to Andy Dalton under center has made the Carolina offense look NFL-caliber again. With an actual threat in the passing game, Hubbard is finding more open spaces.

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RB Kareem Hunt, Kansas City Chiefs: Hunt is back in Kansas City, and he had 14 carries for 69 yards in his season debut against the Chargers. Carson Steele wasn’t getting the job done, and Samaje Perine appears to be the short-yardage and goal-line option. Hunt looks like the volume back, and he is fresh after resting the first three games.

RB Alexander Mattison, Las Vegas Raiders: Mattison has been a touchdown vulture in recent weeks, but in Week 4, he led the team with 60 rushing yards, averaging 12 yards per attempt. Meanwhile starter Zamir White was good for just 2.9 yards per tote. White has had his chance, and soon the depth chart should be changing.

TE Pat Freiermuth, Pittsburgh Steelers: Freiermuth isn’t killing it by any means, but he is doing the one thing nearly every tight end in the NFL isn’t doing, producing consistently. He has at least four receptions in all four games, and his yardage totals have gradually been picking up as he gets more comfortable with QB Justin Fields. They connected for their first score together in Week 4, too.

TE Tucker Kraft, Green Bay Packers: Kraft had six receptions and 77 yards in the first three games combined, but he rolled up six grabs, 53 yards and a touchdown on nine targets in Week 4. He blew past Luke Musgrave on the depth chart and he has emerged as a solid TE1 in most fantasy leagues.

Fantasy football: 5 players to sell in Week 5

TE Mark Andrews, Baltimore Ravens: Coming back from injury, Andrews struggled in the opener, but in Week 2 he started to look like himself with four grabs for 51 yards. All was well, right? Not quite. In the past two games, he has been targeted just once per contest, and he has gone without a catch in both outings. He was once a top-5 option at TE, but he is not usable right now.

WR Brandon Aiyuk, San Francisco 49ers: Aiyuk had a contract impasse during training camp, and has also gotten off to a sluggish start. Cincinnati’s Ja’Marr Chase and Dallas’ CeeDee Lamb had similar situations, but they’re rounding into form. Aiyuk is still rusty, and he is just not getting the job done. He was drafted to be a WR2 in most fantasy leagues, but he is turning in WR4 or flex kind of production.

RB Rhamondre Stevenson, New England Patriots: Stevenson opened with 201 rushing yards and two scores in the first two games. In the past two outings, he has just 19 carries for 66 yards and has lost two fumbles. He has put the ball on the ground at least once in all four games; sooner or later that's going to put him in new coach Jerod Mayo's doghouse.

QB Matthew Stafford, Los Angeles Rams: Stafford has been trying to keep things together, but it’s tough when your top two receivers are injured. He has played a majority of the season without Cooper Kupp and Puka Nacua, leaving Tutu Atwell, Demarcus Robinson and Jordan Whittington as his top targets. Until he gets his big guns back, it’s going to be a slow go.

WR Alec Pierce, Indianapolis Colts: Pierce opened the season with 125 receiving yards and a score, and he also hit the end zone in Week 2. However, his receiving yardage has dropped in every game this season. The return of Josh Downs in Week 3 has bumped Pierce further down the pecking order in Indy.