Del Potro expects great things after Tour Finals run

Argentina\'s Juan Martin del Potro insists he is ready to challenge for Grand Slam titles again after pushing Novak Djokovic to the brink in the semi-finals of the ATP Tour Finals on Sunday. Del Potro was on the verge of a shock win over Djokovic when he led by a set and a break, but the world number one hit back in impressive fashion to win 4-6, 6-3, 6-2 at London\'s O2 Arena. While del Potro was disappointed to see a place in the final slip through his grasp, the 24-year-old took heart from a good week\'s work at the season-ending event. \"Nothing happened to me, Novak just improved his game between the middle of the second set until the end of the match. He deserved to win today,\" del Potro said. \"I played really good in the first two sets, but in the end he made the difference. He\'s the number one in the world so if you don\'t play the whole match at your best level it\'s really difficult to beat him.\" The highlight of del Potro\'s visit to London came when he defeated defending champion Roger Federer to book his place in the last four, ending the Swiss great\'s 12-match unbeaten run at the Tour Finals in the process. That victory, his solid showing against Djokovic and recent titles in Vienna and Basle suggest del Potro is finally back to his best after several years struggling with wrist problems since what was supposed to be his breakthrough in 2009 when he beat Federer to win the US Open. \"These kind of matches give me dreams for the next season,\" del Potro said. \"I beat Roger yesterday. I was close to beat Novak today. I\'m getting closer every day. \"They have been winning all the Grand Slams; Novak, Federer, Rafa (Nadal) and now (Andy) Murray. \"Maybe it could be my big challenge for next year, my big goal, trying to fight for all the Grand Slams with this group.\" Del Potro, who finished as Tour Finals runner-up in 2009, takes great confidence from proving he can compete with the best at such a prestigious event, giving him hope of even more success in 2013 after recording a career-best 65 match wins this year. \"I think I\'m playing good. I don\'t know if I\'m better or not than 2009, but being the semi-finals in this tournament is so big for me,\" he added. \"It was Federer, Djokovic, Murray and me. These big names are there in every big tournament. It\'s going to be my big challenge next year to be part of that group.