Gronkowski fitness a Super Bowl key for Patriots (Reuters) - The fitness of New England Patriots' tight end Rob Gronkowski is looming as a possible game breaker for the February 5 Super Bowl against the New York Giants. Gronkowski, who gained 1,327 yards and scored 18 touchdowns this season, hobbled off the field after hurting his left ankle in Sunday's 23-20 win over the Baltimore Ravens in the AFC title game. The towering 6ft 6in Gronkowski, a receiver too tall for most defensive backs and too fast for powerful linebackers to cover, returned to the fray but eventually left the stadium in a walking boot. He later told reporters he was "good," but his level of involvement in the build up to the Super Bowl will be closely scrutinized ahead of the clash in Indianapolis. New England quarterback Tom Brady has many weapons at his disposal in a high-powered attack that ranked third in the National Football League in points scored, including another productive tight end, Aaron Hernandez, and slot receiver Wes Welker, but knows Gronkowski is his biggest threat. Brady, 34, will be playing in his fifth Super Bowl. He has already won three but his last appearance was four years ago when the Patriots lost 17-14 to the Giants, ending their bid for an unprecedented 19-0 season. "I still can't watch highlights from that game," Brady told a Boston radio station on Monday. Brady was also bothered by his performance on Sunday, saying "I sucked pretty bad" despite scoring what turned out to be the game-winning touchdown in the fourth quarter. The two-time Super Bowl MVP had an off-day passing against the Ravens. After throwing a record-tying six touchdown passes against the Denver Broncos last week, he did not register a single scoring throw and was twice intercepted. An errant pass in the fourth quarter, intended for Matthew Slater in the end zone, was intercepted and gave him a sleepless night after a meeting with Patriots owner Robert Kraft . "He said to me, 'I promise you I'm going to play a lot better in two weeks,'" Kraft told reporters. He's still pretty good in my book.