( CNN ) -- World number two Novak Djokovic extended his winning run in 2011 to 27 matches with a 7-6 6-2 win over Spain 's Feliciano Lopez to win the Serbia Open in Belgrade Sunday . It was top seed and home favorite Djokovic 's fifth title of the year after his wins at the Australian Open , Dubai , Indian Wells and Miami . The 23-year-old Djokovic is now two wins away from equaling Ivan Lendl 's record of a 29-0 winning season start , set in 1986 . Rain interrupted the final twice with Djokovic battling it out on home clay for 73 minutes before wrapping up the first set on a tiebreak . The start of the second set was also delayed by rain before Djokovic secured a pair of breaks to wrap up victory . His last defeat came against Roger Federer in the semifinals of the ATP World Tour Finals last November and he closed out 2010 by leading Serbia to the victory in the Davis Cup final on home soil against France . Djokovic is firmly focused on toppling Rafael Nadal as world number one this season . `` I need to stay healthy and I need to stay fit in order to play well . The winning streak is something I do n't really think about , '' he told the official ATP Tour website . `` I am flattered that people compare me to the greats , like Lendl , ( John ) McEnroe , ( Roger ) Federer , Nadal -- guys who have made history on the tennis court . But I have some other goals to achieve this year . `` Obviously the number one ranking is still far away , even though I 've been winning every match I 've played this year and won five titles in a row . `` But I know I need to do more and if I ever get to that number one in the world it would be a dream come true for me , because it 's been the ambition of my career . '' Argentina 's Juan Martin del Potro is also in fine form heading into the second grand slam of the season at the French Open later this month and secured his second title of the season with a 6-2 6-2 win over Fernando Verdasco in the final of the Estoril Open Sunday . Del Potro , who is returning to his best after missing most of 2010 with a wrist injury , was claiming his ninth ATP title from 12 final appearances . `` This is a great victory , it 's unbelievable to win on clay . It 's something I never expected so soon , '' he told AFP . Former world number three Nikolay Davydenko of Russia won the Munich ATP title Sunday with a 6-3 3-6 6-1 victory over Germany 's Florian Mayer . It was his 21st ATP title and his first since Doha in January 2010 . On the WTA Tour , world number one Caroline Wozniacki began her campaign at the Madrid Masters Sunday with a 6-2 6-3 win over Japan 's Ayumi Morita . Maria Sharapova and Francesca Schiavone also went through to the second round at the tournament which also features the ATP Masters 1000 event with Nadal as top seed . But title holder Aravane Rezai of France lost to Swedish qualifier Sofia Arvidsson 6-3 3-6 6-4 in a shock defeat .
Novak Djokovic wins Serbia Open title to claim fifth crown of 2011 . Straight sets win over Feliciano Lopez extends his winning run to 27-0 . Juan Martin del Potro wins Estoril Open by beating Fernando Verdasco in final . Nikolay Davydenko of Russia wins ATP title in Munich .