Thiem was brushed aside in straight sets by Rafael Nadal in his maiden grand slam final at Roland Garros, but started the grass-court season with a 7-6 (7-5) 6-2 defeat of Russian qualifier Youzhny.

It needed a tie-break to decide the opening set after both players saved a couple of set points and it was the third seed who edged it in Halle courtesy of three consecutive points from 5-4 down.

Thiem played more fluently in the second, easing into a 3-0 lead and later breaking again to set up a second-round encounter with Yuichi Sugita after serving 19 aces and winning 82 per cent of points on his first serve.

Fourth seed Roberto Bautista Agut coasted into the last 16 with a 6-4 6-1 victory over Jan-Lennard Struff.

Kei Nishikori advanced at the expense of Matthias Bachinger, the German qualifier going down 6-3 7-6 (7-3) in his homeland. 

All three German men in singles action went out on day one, Maximilian Marterer having been sent packing by Sugita in three competitive sets. 

Robin Haase and American qualifier Denis Kudla were the other players to make it through.