A bitterly disappointed Tennys Sandgren said it was "back to the drawing board" Tuesday after he missed a golden opportunity to upset the great Roger Federer in their Australian Open quarter-final. The unheralded 28-year-old held seven match points as he pushed six-time champion Federer to the brink, but couldn't find the killer blow and lost 6-3, 2-6, 2-6, 7-6 (10/8), 6-3.

Despite the defeat, it was a gallant effort from a man who likes Melbourne Park, having also made the last eight in 2018. "Tired. Emotionally tired. Physically tired," he said after the gruelling encounter on centre court with the 38-year-old Swiss legend. "I mean, I'm sure I'll look back in a couple days and appreciate the tennis I played the last eight, nine days. But currently just disappointed."

Sandgren has enjoyed a memorable tournament, belying his world ranking of 100 to upset eighth seed Matteo Berrettini and 12th seed Fabio Fognini before running into the Federer roadblock. "It just seemed like his level picked up when his back was right up against the wall," he said of Federer. "He just wouldn't give me anything. Credit to him, for sure."

While Federer won the opening set, the American came roaring back in the second and third sets, with the world number three rattled. Federer fended off three match points at 5-4 in fourth and incredibly, another four in the tiebreaker to take it to a deciding fifth set where Sandgren was overrun. "I've run through them (match points) a bunch of times," said the American. "He was aggressive on one, passive on a few, came in on one, could have put the volley in a different spot. He read it well, hit two good passes. Put me in an awkward spot on the last one I had. All credit to him for sure."

Federer admitted he felt for Sandgren because "I didn't feel like he did anything really wrong". "It's just luck at some point. I've been on the other side, as well," he added.

Asked what he can do to get over the loss, Sandgren replied: "Back to the drawing board. Keep working, keep trying to improve. Maybe I'll get another look, another shot. Maybe I'll come through."