In Ronde Barber's press conference, he talked of retirement feeling right. He said he had made the decision about a month ago, and that he simply did not feel that the effort needed to get his body right for another NFL season was worth it anymore. Perhaps the Tampa Bay Buccaneers' offer to him made the decision a little easier, though.
Stephen Holder of the Tampa Bay Times reports that Barber was offered a $1.5 million salary for a part-time role. Last season, Barber played almost every defensive snap of the season on a $3 million salary. This season, he would have had to make do with significantly less. That makes perfect sense for the Buccaneers, of course. They signed the top free safety on the market and added the best cornerback in the NFL, leaving no room for Barber to play more than a slot cornerback role -- if he could even win that. And a $1.5 million salary isn't bad for a 38-year-old slot cornerback with declining skills.
Ultimately, Barber's decision was his own. The Buccaneers would have taken him back if he wanted to be back, at the right price. They couldn't do more than that: as much as Barber was a centerpiece, the Bucs could not afford to overpay for his services.