A lot can change in a week, and we saw that during week one of the 2015 fantasy football season. Just like that, Peyton Manning looks awful and Marcus Mariota looks like a seasoned pro. Just like that, Joseph Randle is the clear cut guy in Dallas and Andre Ellington is on the shelf. Injuries and poor performances can change player outlooks, roles and our own perceptions of how and where they should reside on our fantasy roster.

To help you better assess your own squads, let’s take a look at five guys on the rise and five more in decline when it comes to their fantasy football stock:

Risers

Marcus Mariota, QB, Tennessee Titans

After being drafted 2nd overall this past April, the crowd seemed to be split on whether or not Mariota would excel in the NFL. It didn’t take long for him to silence the critics as he turned in an impressive preseason along with a tremendous showing in his rookie debut. He emerged in the fantasy landscape and if he continues his 200+ yard, 4 TD production, which he eclipsed by halftime I might add; he can be a fringe starting QB for your fantasy team. He has a solid group of weapons and distributes the ball well. Mariota was 3rd among all QBs in fantasy points this week.

Keenan Allen, WR, San Diego Chargers

While he likely sits in one of your bench slots in week one, the Chargers’ WR went for a league-leading 166 receiving yards and 15 catches, both career highs. Allen’s 17 targets solidified him as the #1 option of Rivers. Just one year removed from a 1,000 yard season, the 3rd year WR looked like a bonafide superstar on Sunday and looks to turn in a breakout year in Mike McCoy’s pass happy offense. Allen is a must-start from here on out.

Donte Moncrief, WR, Indianapolis Colts

As you all know, T.Y. Hilton left the week one affair as the Colts were upset by the Bills. While his injury isn’t major, it will still sideline him for a few weeks. This opens the door for Donte Moncrief, who caught 1 of Andrew Luck’s 2 TD passes. Moncrief was targeted 10 times, more than Andre Johnson as well as the TE tandem of Allen and Fleener combined. Entering the season, Moncrief was already a sleeper in that packed Indy WR corps. In the absence of Hilton, he should emerge as Luck’s go-to-guy in that high powered passing attack.

Tyler Eifert, TE, Cincinnati Bengals

Luckily for Tyler Eifert and the Bengals, his week one performance this past Sunday wasn’t reminiscent of last year where he blew out his elbow and would miss the rest of the season. It wasn’t A.J. Green who torched the Oakland secondary, it was Tyler Eifert who led the team with 9 catches, 104 receiving yards, 2 TDs and 12 targets. The most targeted weapon of Andy Dalton looks to solidify himself as a pivotal piece for that Cincinnati passing game.

Austin Seferian-Jenkins, TE, Tampa Bay Buccaneers

The highly athletic Austin Seferian-Jenkins made some splashy plays in week one as he looks to improve after a disappointing rookie campaign. With 110 receiving yards, he is already more than halfway to last year’s total, and he chipped in with 2 TDs as well. ASJ presents a mismatch with his size and will be a great redzone threat as well. Granted, Mike Evans was out. However, rookie QBs often times heavily rely on their TEs. The Bucs handed the ball off only 20 times and it should be very much of the same from here on out. At the very least he adds good TE depth and presents tremendous upside in your starting lineup.

Fallers

Peyton Manning, QB, Denver Broncos

Unfortunately, Peyton just doesn’t seem to be that reliable fantasy stud that he once was, which can be expected with aging. On 40 pass attempts, he managed to rack up less than 200 passing yards with no touchdowns. He failed to get into a rhythm throughout the duration of the game and didn’t get in sync with his receivers. The Manning that we saw towards the end of last season looks to be what we’ll get in 2015. Hopefully you fantasy owners drafted good insurance.

Melvin Gordon, RB, San Diego Chargers

I was all aboard the Melvin Gordon hype train heading into the season, and even went as far as predicting him as my Offensive Rookie of the Year. However, he went for only 51 yards and nearly split carries in half with Danny Woodhead, who had a much more productive day. While the Chargers had to play “catch up” after falling behind big early on, they passed the ball 42 times as opposed to 28 handoffs. Gordon could see his workload increase in upcoming weeks, but not if Danny Woodhead has anything to say about it.

Calvin Johnson, WR, Detroit Lions

After catching a 28 yard pass on the opening drive, Calvin Johnson brought in just one more catch the rest of the game. While contained by double-coverage most of the game, “Megatron” isn’t the fantasy option that he once was. The Lions don’t look to force him the ball with a new “take what the defense gives us” approach. Johnson was targeted only 4 times, but he remains a vital piece in that Detroit offense. While his production was worrisome in week one, it just wouldn’t feel right to put him on your bench. He remains a must-start, but he needs to pick it up for fantasy owners.

Amari Cooper, WR, Oakland Raiders

Starting Raiders’ QB, Derek Carr was forced to leave the week one game early as he suffered an injury to his throwing hand. While the talent Cooper possesses is undeniable, it doesn’t look like the rookie WR will live up to fantasy expectations, not until Carr is at full strength at least. On 5 catches he compiled less than 50 yards and both passing TDs from backup QB Matt McGloin went to the fullback, Marcel Reece. Fantasy owners who took an early flyer on Cooper should look elsewhere if you have him in your starting lineup.

DaVante Adams, WR, Green Bay Packers

Like Gordon, I was very high on Adams entering the season and stashed him on my bench in the later rounds of the draft. It seemed too good to be true when Jordy Nelson went down with an ACL tear (unless you owned both) as that put Adams in prime position to breakout in that high powered passing offense featuring Aaron Rodgers under center. Adams had already showed great flashes last season and was expected to have a big year, even with Nelson in the lineup.  As it played out in week one, he was the leading receiver for Green Bay with 59 yards, but failed to reach the endzone. Randall Cobb is still the #1 and James Jones emerged with 2 TDs as he already has a rapport with Rodgers. While I expect Adams to reel in some productive weeks, it may not be as soon as some of us had hoped.

About The Author Jonathan Valencia

Jonathan has been investing his time in sports writing for the past decade. Breaking Football's lead writer covers anything from the NFL Draft to providing fantasy football insight. Born and raised in the Jersey Shore. Follow him on Twitter @JonValencia_WiB to talk anything football.