Brandon Marshall claims that NFL players use Viagra as a performance enhancer on the football field.

Adderall has been frequently cited as the reason for players testing positive for performance enhancing drugs in recent weeks.

The six teams with the best turnover differential in the NFL have a combined record of 43-23.

The New England Patriots are plus-24 in the category, followed by the Chicago Bears and New York Giants with a plus-13.

The bottom-six teams have a combined record of 27-38. 

The Kansas City Chiefs are minus-21 on the season.

Matt Forte left Soldier Field on Sunday in a walking boot after injuring his ankle in the Chicago Bears' 28-10 win over the Vikings.

Forte suffered a sprained ankle in Week 2 and missed one game.

Michael Bush will receive a bulk of the carries in Forte's absence.

"I've been in the league long enough that when that happens, I'm always ready,'' Bush said.

Bush has 60 yards and two touchdowns on Sunday.

Jay Cutler has been cleared to return from his concussion and is expected to start for the Chicago Bears on Sunday against the Vikings.

Cutler underwent an evaluation Saturday by an independent neurologist.

"He has progressed as we wanted him to do," Bears coach Lovie Smith said after practice. "As I've said, it's looking good. One more step to get him evaluated by an independent neurologist. Jay Cutler is getting better, was able to do more than he did yesterday."

Mike Tice will remain the playcaller of the Chicago Bears.

With the offensive line struggling of late, it has been suggested that Tice focus on improving that unit.

"There's no consideration at all on that," Lovie Smith said. "I don't know where you [the media] got that from. I doubt if Mike really said that but if he did, I can stop that right now. That's not part of it at all.

" Mike works with the offensive line quite a bit with [offensive line coach] Tim Holt. We need to do a better job with it, like we all need to do a better job. Beyond that it's just business as we've been doing."

Alex Smith will not play for the San Francisco 49ers on Monday against the Bears. Smith did not receive clearance on his contract test following a concussion last week.

Colin Kaepernick will start for the 49ers.

Jay Cutler is also out, leaving Jason Campbell to start at quarterback for the Bears.

Mike Ditka suffered a "very minor stroke" on Friday and was hospitalized.

"I feel good right now and it's not a big deal," said Ditka.

Ditka has not had any major health problems in recent years. But in 1988 when he was coaching the Bears he suffered a heart attack.

Ditka is currently an analyst at ESPN.

Jay Cutler has been ruled out by the Chicago Bears for Monday's game against the 49ers.

Jason Campbell will start at quarterback.

Cutler suffered a concussion against the Texans on Sunday, his second since coming to the Bears.

The San Francisco 49ers have dropped from 13th to 31st in the NFL in kickoff coverage and from 11th to 20th in covering punts.

Some of that drop has been attributed to the departure of Blake Costanzo, who signed with the Beras in the offseason.

“It’s only human, man,” Costanzo said. “… I won’t deny, it’s not the year (the 49ers) had last year. But they’ve still got pretty good players. They’ve still got (special teams) Coach (Brad) Seely. I just think some other guys are going to step up and be leaders for them and bring the group together and make it as important as it was last year.

“You know, I never wish ill upon anybody or anything like that, but maybe sometimes people can understand that it’s more than just the football player. It’s more than just making plays out there. People are leaders in the locker room.”

The Bears signed QB Josh McCown and waived TE Brody Eldridge on Tuesday.

McCown has started 33 of 50 games played in nine NFL seasons with the Cardinals (2002-05), Lions (2006), Raiders (2007), Panthers (2008-09) and Bears (2011) after entering the league as a third round selection (81^st overall) by Arizona in the 2002 Draft. 

In three games (two starts) for the Bears last season, McCown completed 35 of 55 (63.6 percent) passes for 414 yards, two touchdowns and four interceptions, including 470 total yards (402 passing and 68 rushing) in his two starts.