In fact, negotiations can't even begin with Worilds until March 22, 11 days after free agency begins March 11. That, and not the idea of the Steelers having five days to match any offer he is given, is what will really stall any team's effort to sign Worilds, considering the allure of signing other more readily available players at the start of free agency, as well as other Pro Days highlighting the 2014 NFL Draft class.
The Steelers' main priority in all of this would be to sign Worilds to something of a long-term deal. If they're willing to put that large of a cap hit on themselves in one year, it seems logical to assume they're interested in keeping that player long-term. Getting Worilds signed to an extension now would likely free up a large chunk of cap space - something that will likely be done through multiple other moves in the coming days.
In doing it, the Steelers are really buying themselves protection over Worilds jumping ship while the team is theoretically in the middle of negotiating with other players. Last year, cornerback Keenan Lewis signed with the New Orleans Saints in free agency, and perhaps the Steelers would have given him a deal similar to the one the Saints offered had they had time to do so.
That's a hypothetical, but it's reasonable to believe the Steelers just needed that extra window of time to get a few other contracts set up before making an offer to Woodley, including a possible restructured deal with Ike Taylor and LaMarr Woodley (not unlike the one the team allegedly set up with Heath Miller Monday), a contract or restructure with Troy Polamalu and an extension with Ben Roethlisberger.
The Steelers would have a much clearer salary cap picture with conclusions coming on the situations of those players. Perhaps the window of time afforded to them by placing the transition tag on Worilds gives them that.