Israel’s Dudi Sela goes for his 20th career title on the Challenger circuit on Sunday when he faces China’s Di Wu in the final in Shenzhen, China.The 30-year-old Israeli, ranked No. 84 in the world, cruised into the final with a 6-1, 6-2 win over Adam Pavlasek (126) of the Czech Republic on Saturday.Sela, who could climb almost 20 places in the new rankings with a win, is targeting his first title of the year, losing in the final in Happy Valley, Australia in January.Wu (175) beat Italy’s Thomas Fabbiano (110) 6-2, 1-6, 7-6.Meanwhile, Novak Djokovic barely got out of first gear but had more than enough in the tank to beat Briton Kyle Edmund 6-3, 6-3 in the second round of the Miami Open on Friday.The top seed, who is trying to join Andre Agassi as a six-times Miami winner, improved his record since the start of 2015 to 105-7, picking up 14 titles along the way.Just five days after an emphatic victory at Indian Wells, the Serb adjusted well to the steamy conditions in south Florida. He was broken once, in the first set, but broke 21-year-old Edmund four times.Earlier in the day, Juan Martin del Potro had two surprises -- the first when his scheduled opponent Roger Federer withdrew with illness, and the second when he fell 6-4, 6-4 to lucky loser and fellow Argentine Horacio Zeballos. Briton Andy Murray, Spaniard Rafa Nadal and Japan’s Kei Nishikori were all in action on Saturday.Federer’s return from knee surgery will have to wait after the Swiss maestro withdraw from his second-round match because of a stomach virus.Federer, sidelined for almost two months after tearing his meniscus, was due to play del Potro in a repeat of the 2009 US Open final.“I feel bad for the tournament and the fans, as I have rarely ever had to withdraw at such short notice,” the third-seeded Federer said in a statement.“I have not felt great for a few days, and unfortunately it got worse in the last 24 hours. I was really excited to have my comeback in Miami but am in no condition to play. I tried to warm up this morning, but it was clear that I could not compete.”The 34-year-old Federer said on Thursday that he had injured his knee in a freak domestic accident after slipping while running a bath for his twin daughters following his semi-final defeat at the Australian Open at the start of 2016.Fifth-ranked Rafa Nadal said he was disappointed Federer had to withdraw. “It’s obvious that a tournament with Roger is always better,” the Spaniard said. “It’s good that it’s a stomach problem and at the same time it is not the knee, so it’s not a big deal. But it’s obvious that it’s terrible news for the tournament.”Reuters contributed to this report.