Top seed Juan Martin del Potro will face qualifier Grega Zemlja for the Austrian Open title today after the Slovenian world number 70 stunned Serb second seed Janko Tipsarevic in yesterday’s semi-finals. Argentina’s del Potro reached his second consecutive final in the Austrian capital as he defeated Luxembourg’s Gilles Muller 7-6 (7/4), 7-6 (7/5) in a duel which featured 33 aces. Zemlja, meanwhile, pounced on an injured Tipsarevic to win 3-6, 7-6 (7/5) 6-2 in just over two and a half hours in his first career semi-final. Tipsarevic began feeling an old injury in his right shoulder in the second set as Zemlja climbed back into the contest. The Serb was unable to stop his inspired opponent’s momentum as Zemlja won the second set after Tipsarevic gifted a double-fault for two set points. In the third, Zemlja went up two breaks and earned the biggest win of his career on a second match point as a Tipsarevic forehand clipped the top of the net. “I played a great match, it was really difficult in front of such a big stadium filled with people,” said the winner. “It was very emotional for me, it felt super. “It was a tough match against a top player like Janko and it came down to the last point.” Tipsarevic, who is chasing a place in the season-ending World Tour Finals in London next month, was disappointed with his performance. “I was too passive, waiting for him to make mistakes,” said the second seed, “I haven’t felt my shoulder problem for the past 18 months but it suddenly started bothering me. “In the second set I was struggling on serve, I didn’t have the freedom to toss, I was just throwing it up where it did not hurt. My disappointment is huge.”