He will have to have a range of voices—from the nails-on-chalkboard orations of Skip Bayless to someone more highly regarded, like Ross Tucker of the NFL Network. Reporters like Adam Schefter will also pop up and comment on rumors that actually have basis in the the league you're running, such as players you're scouting for the upcoming draft.
Pastapadre today compiled all of the real-world media types who'll be "tweeting" in this video game. It doesn't appear that they will be doing so under their official Twitter handles. Screenshots show the tweets coming from alternate accounts with an "EA" appended to them. This probably is because the suite of online features in "Connected Careers" allows for your league to publish news through its own virtual Twitter feed, presumably letting you follow its developments from work the same way you would the real NFL's.
Here are all of the media personalities appearing in the virtual Twitter of Madden NFL 13's "Connected Careers".
Mike Hill (ESPN)
Trey Wingo (ESPN)
Ross Tucker (NFL Network)
Mark Schlereth (ESPN)
Matt Miller (Bleacher Report)
Scott Wright (DraftCountdown.com)
Robert Flores (ESPN)
Skip Bayless (ESPN)
Susannah Collins (Inside the NFL)
LaVar Arrington (former player, CBS Radio)
Todd McShay (ESPN)
Chris Mortensen (ESPN)
Adam Schefter (ESPN)