BRETT FAVRE, 2009 VIKINGS
The only age-40 QB to start every game—no one else has started more than eight—Favre finished his 19th and penultimate season with the most passing yards (4,202) and TDs (33), plus the best passer rating (107.2), of any quadragenarian in history. He also had the fewest regular-season INTs (7) and lowest pick percentage of his career (1.3%). Alas, even though he's the only 40-year-old QB to win a playoff game, he'll be remembered for the fourth-quarter interception that ended the Vikes' Super Bowl quest in the NFC title game against the Saints.
MATT HASSELBECK, 2015 COLTS
He took over for the injured Andrew Luck in October and won the first four of his eight starts before a barrage of injuries (shoulder, neck, ribs, jaw) led to his end-of-season retirement.
SONNY JURGENSEN, 1974 REDSKINS
Washington went 3--1 when Jurgensen started in place of Billy Kilmer, but he wasn't the change of pace they needed in the divisional round against the Rams. In what would be his last NFL appearance, he threw three second-half INTs (on 12 attempts) and sunk the Skins.
VINNY TESTAVERDE 2003 JETS
Testaverde went 2--5 in his penultimate season with the Jets, but Father Time hadn't quite turned on him yet: He threw seven TDs against just two interceptions. His last four years were far more quadragenarian in nature: 24 TDs and 32 INTs.
WARREN MOON 1996 VIKINGS
He won four of eight games before giving way to Brad Johnson—another QB who later played (poorly) at age 40—and finished with more INTs (nine) than TDs (seven). Remarkably, he was actually better a year later, when he led the league with 245.2 ypg and went 7--7 with Seattle.