Juan Martin Del Potro. Pic/AFP

Former US Open champ Juan Martin Del Potro stepped up his bid for a second straight tournament victory as he clinched a place in the semi-finals of the ATP Indian Wells Masters on Friday. The world number eight, who won a title earlier this month in Acapulco, Mexico, fended off a stern challenge from Germany's Philipp Kohlschreiber with a 3-6, 6-3, 6-4 win. For Del Potro, reaching the semis is another feather in the cap of his comeback from injuries as he is back in the top 10 for the first time since 2014. "It wasn't an easy match as everyone could see," the 2009 US Open champion said.