German ace Alexander Zverev has been stunned in three sets at the Swiss Indoors semi-final stage as he lost 6-3 6-7 (6-8) 6-4 to qualifier Marius Copil in Basel.

Zverev had three chances to break the 28-year-old Romanian in the first set on Saturday but after the German’s awkward overhead shot flew long from the back of the court, Copil broke through with a scorching forehand to lead 4-2 before he served out the first set.

The second set was much tighter between the pair but Zverev looked in trouble as he trailed 4-2 in the tie-break.

However, Zverev won three straight points and then extended his time in Basel for an extra set by outlasting Copil in a rally.

The 21-year-old world number five had to serve to stay in the match at 5-4 in the third set.

But a vicious backhand opened up match points for Copil who emerged victorious after 2 hours 31 minutes with a determined volley to enter his first senior level final.

Copil, ranked 93rd in the world, will meet either eight-time winner and title holder Roger Federer or Russian Daniil Medvedev on Sunday.