The New England Patriots have signed Pro Bowl linebacker Jerod Mayo to a five-year contract extension, a league source told ESPN NFL Insider Adam Schefter on Saturday.Mayo, despite missing two games in October with a sprained knee, ranks third for the Patriots with 68 tackles this season after a year in which he logged a career-best 175 and was voted to his first Pro Bowl. He was the AP's defensive rookie of the year in 2008. News of the signing comes six days after Mayo pulled in his second interception in as many weeks in a win over the Washington Redskins. His previous interception, in a win over the Indianapolis Colts, had been the first of his four-year career. Source: ESPN.com