Tennys, like Federer, has a SA-born mother!

Cape Town - The 2018 Australian Open’s surprise package, Tennys Sandgren, has a South African connection.

The unheralded American on Monday upset Austria's fifth seed Dominic Thiem to advance to the quarter-finals of the tournament in Melbourne.

The 97th-ranked Sandgren won 6-2, 4-6, 7-6 (7/4), 6-7 (7/9), 6-3 in just under four hours to continue his extraordinary Australian Open run which included a win against former champion Stan Wawrinka earlier in the tournament.

According to Netwerk24, Sandgren’s mother, Lia Sandgren, née Lourens, was born in South Africa.

The Afrikaans website reported that Lia grew up on the farm Broodsnyersplaas between Bethal and Middelburg in Mpumalanga.

She matriculated at Hoërskool Middelburg before obtaining a Bachelor of Music degree (BMus) at the University of Pretoria.

She met Tennys’ dad, David, at a tennis club in Johannesburg and the family moved to Nashville, Tennessee in 1988.

Tennys’ dad was a tennis coach, but passed away in 2011.

Sandgren became just the second man in the last 20 years - since Frenchman Nicolas Escude - to make the quarter-finals on his Australian Open debut.

Amazingly, the 26-year-old missed out on even qualifying for the main draw in the past four years in Melbourne.

Sangren is not the only ATP Tour star with a South African bond, with world No 2 and 19-time Grand Slam winner Roger Federer also boasting a mother born in the country.

"I don't know if this is a dream or not," Sandgren was quoted as saying by AFP after beating Thiem on Monday.

"He played some really great tennis, especially in that fourth set tie-breaker.

"I knew I had to take my chances. I knew that behind the court he could probably outlast me and out-grind me, he's a heck of a player.

"So I knew I had to come out and play aggressive and take my chances and serve well and thankfully it worked out in the end."

In the quarter-finals, Sandgren will face South Korea’s Chung Hyeon, who stunned former world No 1 Novak Djokovic 7-6 (7/4), 7-5, 7-7 (7/3) in their round of 16 clash.