Here are three players whose Week 7 successes should be ignored:

WR Nate Washington, Texans (vs. Titans)
Washington had an incredible fantasy line in the Texans' Week 7 drubbing at the hands of the Miami Dolphins, racking up nine catches for 127 yards and two TDs. You might think with the injury to Arian Foster that Washington is poised for great success. And you would be wrong.
DeAndre Hopkins is the best option in Houston by a country mile, and while the team leads the NFL in pass attempts, Washington is far too inconsistent. The odds of him reaching the heights of Week 7 again are very low. He may produce the occasional return for a low price, but don't hitch any real expectations to his wagon.

RB Darren McFadden, Cowboys (vs. Seahawks)
McFadden has definite value. He's inexpensive - though that could change in coming weeks - and has been included in Dallas' passing game keeping him relevant should the Cowboys fall behind. His 152 yards rushing in Week 7 on 29 carries were season highs. With Lance Dunbar sidelined, he will likely continue to get the lion's share of the carries.
Like the aforementioned Washington, McFadden's bandwagon should be avoided because he'll only let you down. He isn't getting touches in the red zone and he's never shown consistency throughout his career. His season's ceiling has probably been reached even if he can provide a serviceable return at the FLEX position.

RB Mike Tolbert, Panthers (vs. Colts)
Tolbert found the end zone twice against the Eagles in Week 7. He ran one in and managed a two-yard reception. That sounds good. What doesn't is his grand total of 18 all-purpose yards from scrimmage.
The TDs might convince some he has become a viable option, but he can't be trusted on a week to week basis. Jonathan Stewart is still the lead back. Tolbert will probably nab a score here and there through the end of the season, but he's unpredictable and more likely to be irrelevant in DFS.