The 20-year-old needed four match points to eke out a 7-6 (6), 4-6, 7-5 win - his first in three FedEx ATP Head2Head meetings with the Argentine.
Chung, who sensationally reached the Australian Open semis, was too good for qualifier Franko Skugor 6-4 7-6 (7-4).
That followed a three-set victory over the young American, ranked 91st in the world, in Acapulco previous year. The younger and lower-ranked player was more efficient on his first serve and he won nearly 50 per cent of the return points to create 11 break points, converting four to score a straight sets win. He falls, however, to Gojowczyk in his second match at the Delray Beach Open. With two victories this week, he has doubled his 2017 win total.
"I've got to definitely review it, think about it, because that was a pretty poor level I put out there today". I've had a tonne of tough losses against top guys.
In the quarters he will face Australian Open semi-finalist Chung, ranked 30th in the world, for the first time. "He made three straight first serves, and he hit a insane, high, backhand drop shot, angle thing on the first match point, which was a good shot".
Top seed and defending champion Sock was the biggest casualty, upstaged by wildcard and fellow American Reilly Opelka 4-6, 7-5, 6-3 at the ATP 250 tennis tournament. "I think both of us were playing well".
"There were a lot of times in the match where I was down and he had break points, and it could have really gone either way, and I came up in those moments in the match and that really made the difference", Fritz said.