Chocolate-loving Dominic Stricker caused a major upset at the US Open by knocking out seventh seed Stefanos Tsitsipas.

The 21-year-old qualifier from Switzerland, ranked 128 in the world, stunned two-time grand slam finalist Tsitsipas with 7-5 6-7 (2) 6-7 (5) 7-6 (6) 6-3 victory to reach the third round.

Stricker is a former French Open junior champion who recently admitted his coach had told him to cut down on chocolate and cookies but it was Tsitsipas who was left feeling sour after a four-hour slog on the Grandstand Court.

“You know, I came out today pretty well today and felt good from the first set,” said Stricker.

“Over four hours it was a tough battle and I’m just super happy right now. I’m going to enjoy the rest of the day and recover tomorrow.

“It’s such a great day for me and such a great win. It gives me a lot of confidence. I believe a lot in me now.”

Remarkably, Stricker could have been on the plane back to Bern last week having faced a match point in the second round of qualifying.

He has now achieved his best result at a grand slam, having bettered his run to the second round at Wimbledon earlier this summer.

Tsitsipas served for the match at 5-3 in the fourth set, and the Greek said: “That hasn’t happened to me before. It’s the first time for me.

“Usually I’m much tougher mentally, and I have shown it by coming back. Even though sometimes I get broken serving for the match, let’s say, I still find ways in the tie-break or perhaps in the fifth set. Today was not the case.”

Second seed Novak Djokovic is safely through to round three after demolishing Spain’s Bernabe Zapata Miralles.

The Serbian, chasing a 24th grand slam title, dropped just six games in a 6-4 6-1 6-1 victory.