Juan Martin del Potro squeaked into the semifinals of the ATP World Tour Finals by beating Roger Federer 6-2, 6-7 (5), 6-3 Thursday _ the slimmest possible margin to advance and knock Andy Murray out of the tournament.
That result means Del Potro and Federer both advance after a three-way tie in Group A. All three players finished the round-robin stage with two wins and identical 5-4 set records. However, Murray was eliminated after winning the lowest percentage of games. Had Del Potro lost just one more game against Federer, Murray would have advanced at the Argentine's expense.
Murray beat Fernando Verdasco 6-4, 6-7 (4), 7-6 (3) earlier Thursday.
