MIAMI – Roger Federer survived a scare to beat teenager Ryan Harrison and reach the third round of the Miami Masters.The 16-time Grand Slam winner breezed through the first set, before letting a 5-2 lead slip in the next as the 19-year-old American forced a tie-break.Federer, who won at Indian Wells last week, completed a 6-2 7-6 (7-3) win and now faces Andy Roddick in the last 16.Top seed Novak Djokovic beat Marcos Baghdatis 6-4 6-4 and next meets fellow Serbian Viktor Troicki. Troicki rallied to beat qualifier Guillermo Garcia-Lopez 4-6 6-1 6-4. Roddick, who did not face a break point as he beat Gilles Muller of Luxembourg 6-3 6-2, has dropped to 34th in the world rankings, the lowest he has been since 2001.He has won only two of his 23 matches against Federer but did beat him at this event in 2008."There’s no getting around the fact that he has been the biggest obstacle in my career,” 29-year-old Roddick said. "His game matches up well against mine.”Number five seed David Ferrer also booked his place in the third round, beating Bernard Tomic in straight sets 6-4 6-4, while eighth seed Mardy Fish defeated Frank Dancevic 6-3 7-6.