DOHA: Pierre Lasogga struck a brace as Al Arabi became the first side to book a place in the Amir Cup semi-finals with a 3-0 win over Al Ahli .   The quarter-final encounter at the Abdullah bin Khalifa Stadium was a lopsided affair as Arabi completely dominated an Al Ahli side, which struggled for full 90 minutes. The scoreline could have got much worse for Ahli, but for some poor finishing by Arabi players. Ahli’s defence was shambolic on the night, as they were beaten for pace repeatedly by forwards Lasogga and Hamdi Harbaoui.   Arabi, who are unbeaten in four matches in QNB Stars League, had defeated Ahli twice in the league this season and the Heimer Hallgrimsson’s men maintained the stronghold on their rivals.   Arabi went 1-0 up in the sixth minute after Ahli’s Mohamed Abdulnaser al-Abbasi gave the ball away in the midfield which was latched on to by Ahmed Fathi Abdulla. The Arabi skipper then found Lasogga, who beat goalkeeper Ivanildo Rodrigues in one-on-one with a cool finish.   Arabi’s lead increased in the 22nd minute with Abdulla and Lasogga involved in the action again. Abdulla charged from the right hand side and struck fiercely, which brushed past Rodrigues and hit the post. The rebound, however, fell into the lap of Lasogga, who tapped into the empty net.   With momentum in their side, and Ahli midfield and defence totally disorganised, Arabi went for the kill but Harbaoui wasted couple of easy chances.   The second half played out in a similar manner, with Arabi enjoying most of the possession. In the 58th minute, Harbaoui spurned a golden opportunity but with just Rodrigues to beat the Tunisian forward’s heavy touch sailed into the stands.   Ahli had a rare chance to score in the 60th minute as captain Nabil El-Zhar found himself in the Arabi box, but took one too many touches before shooting wide. Arabi sealed the game in the 69th minute, with substitute Khalaf Saad Khalifa finding the net after a deflection off a defender. Lasogga had a chance for hat-trick in the 72nd minute but the German forward’s strike came off the post.