World No. 64 Dominik Koepfer admitted he regrets for missing out on a chance to beat Roger Federer at the French Open but added playing the Swiss at a Grand Slam tournament was still a nice memory. Koepfer, 27, competed extremely well against Federer when they met in the French Open third round last year but it was the 20-time Grand Slam champion that won 7-6 (5) 6-7 (3) 7-6 (4) 7-5. After winning the second set, Koepfer had a 4-2 lead in the third set but failed to hold on to his serve and win go up by two …