There was a bizarre incident at the start of the fourth set when a malfunction by the electronic line call system meant 'fault' was called during play, and the point was replayed.

But it didn't impact Fritz's return to form as he dug deep to come out on top of a tie-break and progress with a 6-3 6-4 1-6 7-6 (7-4) victory over the Russian.

"I'm feeling great to get through it," he said in his on-court interview.

"The match was going so well for me for two sets. I've never had a match really just flip so quickly, so I'm really happy with how I came back in the fourth set and got it done.

"I felt I couldn't miss and then all of sudden I'm making a ton of mistakes. Momentum was definitely not going to be on my side going into a fifth."

World number five Fritz is looking to end his country's long wait for a male Grand Slam winner, with Andy Roddick the last to achieve it with a 2003 US Open success.

But Fritz will face another tough test in the last four in the shape of either defending champion Carlos Alcaraz and Britain's Cameron Norrie.