Klizan had never beaten Wawrinka in three attempts, but the Slovakian came from a set down to win 4-6 6-3 7-5.

The unseeded Klizan was broken in the opening game of the first semi-final, but claimed the only break of the second set to force a decider.

There was not much in it in the final set as Wawrinka got back on serve at 3-3, only for 2012 champion Klizan to break again for a 6-5 lead and serve out the match.

Left-hander Klizan has won all six finals he has featured in — including one at the Generali Open last month — but Thiem will be the favourite to take the title.

The No.1 seed knocked out Roberto Bautista Agut, winning 6-4 6-3 to move one victory away from a third tournament triumph of the year.

World No.8 Thiem had also lost all three encounters with Bautista Agut, yet it was a different story this time around as he served superbly and broke once in each set to reach his first hard-court final for two years.

Nishikori's hopes of claiming a first tour-level title since 2016 were ended by world No.166 Bachinger, from Germany, at the Moselle Open in Metz.

Bachinger defied the odds to reach his maiden final at the age of 31, winning 2-6 6-4 7-5, and will come up against home favourite Gilles Simon, who saw off Radu Albot 6-3 6-1.