A Challenge Not Taken, a Match Not Won Li Na made a mistake that contributed to own demise against Agnieszka Radwanska in the quarterfinals at Wimbledon on Tuesday. Radwanska won a hard-fought battle, 7-6 (5), 4-6, 6-2, but Li helped her by not challenging a critical call that enabled Radwanska to steal the opening set. The outcome of many matches can be traced back to a single point. In this case, Li had set point in the opening set, serving at 5-4, ad in. Li had already failed to convert two set points in the game but forced a backhand error from Radwanska with a big forehand approach to gain her third opportunity to put the first set to bed. She walked up to the baseline and bounced the ball three times and tossed it high in the air, but too far to her left, and caught the toss and reset. Three more bounces and Li was good to go. She crushed a first serve that caught the sideline, but it was called a fault by a linesman directly behind Radwanska. Li immediately looked to the umpire and asked, "It was out?," while nodding. Her body language and questioning were polite - too polite - given the importance of the situation. Li still had her full complement of three challenges to burn. There may not have been a better time in her entire career to use one. It was set point; the serve was incredibly close, so let one fly. Li is a former French Open champion and twice a finalist at the Australian Open. She is a seasoned competitor who turned pro in 1999, has won almost 300 matches and has banked around $11 million in prize money. With all that experience and with a Wimbledon title in her sights, the no-brainer decision was to challenge the call. Best to know for sure than go with the guess of a linesman. But Li didn't challenge and eventually lost the point when she guided a tentative overhead straight at Radwanska, who crushed a backhand passing shot winner down the line. Careers can be defined by fleeting moments in time. If Li challenges, she wins the set. She didn't, and she ended up losing it. Li was asked later if the serve was in or out. Was in? Li asked back. The interviewer said, "Yes." This was the first time Li found out the first set should have been hers. Li was asked why she didn't challenge the call and said, "Next time I will challenge it for sure." With Li's talent, the odds are that there will be a next time, but as every athlete understands, you never really know if a next time will roll around. Li also had a fourth match point serving at 5-4 but netted a forehand that came deep and hard from Radwanska. Li also led by 3-1 and 5-3 in the opening-set tiebreaker, but when she put a backhand in the net to lose the tiebreaker, 7-5, you could feel that a golden opportunity had slipped away. Li converted both her break points to win the second set, 6-4, but she went 0 for 4 on break points in the third set while Radwanska, who will play Sabine Lisicki in the semifinals, won 2 of 9. A point here and a point there may not seem like such a big deal, but they are the building blocks of careers and spectacular bank accounts. Is it a stretch to say that if Li challenges the call and wins the first set she then wins the match and goes on to win the tournament? Maybe it is - but more important, maybe it isn't.