US Open champion vanquished: Teenager Zverev stuns Wawrinka to win St Petersburg Open

German teenager Alexander Zverev won his first ATP Tour singles title with a 6-2 3-6 7-5 upset win over Switzerland's world number three Stan Wawrinka at the St Petersburg Open on Sunday.

Top seed Wawrinka, playing in his first tournament since winning the U.S. Open, was shocked by the fifth-seeded 19-year-old who quickly took the opening set. The Swiss, who was looking for his fifth title in what has been an excellent season, levelled the match by taking the second against the world number 27.

Things looked to be going Wawrinka's way when he led with a break in the third but Zverev, who had lost his previous two ATP finals, was not going to let history repeat itself a third time. The big right-hander produced some excellent tennis to storm back and claim victory in just under two hours and 30 minutes.