Defending German champions Borussia Dortmund opened the new season with an impressive 3-1 win over Hamburg on Friday thanks to goals from two of Germany's rising stars. Goals either side of half-time by midfielder Kevin Grosskreutz, plus a superb individual effort from 19-year-old prodigy Mario Goetze, who barely put a foot wrong all game, sealed the three points. Hamburg gave the hosts a brief scare with just over 10 minutes left when midfielder Robert Tesche headed home for a consolation goal. But having dominated the league from the end of October, Dortmund picked up where they left off at the end of last season at the sold-out Signal Iduna Park in May -- then, as now, they played in front of a capacity 80,720 crowd. With Bayern Munich in action on Sunday, when they host Moenchengladbach, Dortmund's young guns -- the squad has an average age of just 24.9 years -- remain the team to beat in Germany. Goetze has been called up for Wednesday's international friendly against Brazil in Stuttgart and on this showing it was easy to see why. Dortmund's new midfield signing Ilkay Gundogan, who is also in the Germany squad, had a quiet league debut by comparison having joined from Nuremberg. The champions made their early pressure pay off when a neat pass from Goetze put Grosskreutz in space and the left wing drilled his shot past Hamburg goalkeeper Jaroslav Drobny on 17 minutes. Japan midfielder Shinji Kagawa hit the post and fired wide in the opening stages after finding plenty of space in the Hamburg defence. Dortmund made it 2-0 with less than half an hour played when Goetze played a neat one-two with Poland striker Robert Lewandowski and chipped his shot past Drobny to put the hosts in firm control. Grosskreutz made sure the champions kicked off the new season with a win when he stabbed home after a goalmouth scramble on 48 minutes. From a corner, Goetze popped up again to play a one-two with Kagawa and when the ball bobbled into Grosskreutz's path, he fired home at the second attempt. Hamburg gave the hosts a brief scare when Tesche headed home on 79 minutes after Kagawa had earlier cleared off the line.