DENVER (CBS4)– One day after the National Football League announced it was investigating Peyton Manning for performance enhancing drug use, the quarterback reiterated the claims were false.

“I welcome (the investigation) and (the allegations are) garbage from the first day it came out and it’s still garbage today,” Manning said at the beginning of his Thursday press availability.

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Manning was accused in December 2015 of using Human Growth Hormone while recovering from neck surgery in 2011 by an Al Jazeera America documentary. Manning has denied the claims and has threatened to file a defamation lawsuit which other players named in the documentary have already done. The accuser in the documentary has recanted what he was seen saying on hidden camera.

“It’s one of those things where there’s a lot of smoke but not much fire. And it’s suggestive. It does force Major League Baseball and the NFL to follow up and investigate,” Dr. Roger Pielke Jr. said about the documentary.

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Pielke is a professor at CU Boulder and studies all kinds of corruption in professional sports.

“This is where having an independent body to investigate these sort of allegations would serve the athletes well. It would serve the NFL well. As we saw with Tom Brady and his deflated footballs sometimes the NFL isn’t the best at internal investigations,” Pielke said.

The timing of the NFL’s investigation is another similarity to the drama Tom Brady and the New England Patriots were forced to go through in preparation for their Super Bowl last season. But if Manning retires the investigation could be pointless.

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“The fact that there isn’t an independent body like a USADA, the U.S. Anti-Doping Agency, to oversee the NFL makes it a sort of situation where there’s rumors and allegations and speculation that are very hard to sort out,” Pielke said. “In Peyton Manning’s case, the worst case scenario is a hit to his reputation because the formal sanction is as little as four games if he were to be found guilty. It probably won’t matter in the same way that the deflate gate doesn’t matter to Tom Brady’s legacy and it speaks to the seriousness to which the NFL takes performance enhancing drugs. It’s much more of a talking point ahead of the Super Bowl than it is a serious issue that Peyton Manning has to deal with.”