South Korea’s Chung Hyeon knocked out Britain’s Cameron Norrie and American Jack Sock beat Australia’s John-Patrick Smith in the first round of the Delray Beach Open.

Eighth seed Chung recovered from losing the first set to dismiss British number three Norrie 3-6 6-3 6-1 on the first day of the Florida tournament.

The 22-year-old Briton had looked like he might cause an upset against last month’s Australian Open semi-finalist when he took the opening set, however Chung fought back with a dominating display.

Norrie tweeted: “Delray Beach…tennis is not easy. Mexico next.”

World number eight Sock easily saw off number 225 Smith 6-4 6-4 as the top seed took his first win of 2018.

Meanwhile American wildcard Frances Tiafoe beat Australian Matthew Ebden 6-2 2-6 6-2 and American Donald Young beat India’s Ramkumaar Ramanathan 6-1 6-2.

At the Rio Open Croatian world number three Marin Cilic comfortably progressed into the second round with a 6-3 6-2 win over 139-ranked Argentinian Carlos Berlocq.

But there was disappointment for local Rogerio Dutra Silva, the Brazilian number 86 losing to Spaniard Albert Ramos-Vinolas 6-3 3-6 6-4.

American Australian Open quarter-finalist Tennys Sandgren also progressed after Roberto Caraballes Baena retired.

In the south of France Bosnian Damir Dzumhur beat Kazakhstan’s Mikhail Kukushkin 7-6 6-7 1-6, while Frenchman Julien Benneteau defeated Malek Jaziri  6-4 6-3 to progress to the second round of the Open 13 Provence.