It's all good. I'm very happy I got out of that first set, it ended up being the key to the match.
The two veterans had a great year in 2017 and showed that they still have what it takes to make it to the finals of a grand slam and win.
He was keen not to take away from the glasses-wearing Chung's huge achievement after the 21-year-old followed up his win over fourth seed Alexander Zverev in the last round.
With Chung already through, and Kyle Edmund playing No. 6 Marin Cilic in the other half of the draw, it's the first time since 1999 that multiple unseeded players have reached the Australian Open semifinals. A couple of weeks ago, he defeated the 26-year-old American in the first round of the ASB Classic in Auckland, New Zealand, 2-1 (6-3, 5-7, 6-3).
Before the quarter-finals started, Federer was the favourite to win the Australian Open.
Two break points came and went for Federer - one after a Federer challenge couldn't be reviewed because the technology didn't work.
Federer was broken in his opening service game and fell behind 2-5 before he broke back with a backhand in the ninth game to send the first set into a tiebreaker.
After the first-set dramas it was routine with Federer breaking decisively for 5-3 with an easy backhand victor after Berdych's half volley sat up begging.
The Romanian reeled off nine games in a row and 12 of the last 14 games to recover from 0-3 en route to a 6-3, 6-2 victory on Rod Laver Arena. "I'm really happy that I could find the rhythm back because is not easy when you are very exhausted", Halep said.
Roger Federer is also the only remaining semifinalist from previous year.
"I thought he played very well".
"The key at the end was that I really could run forever".
Berdych and Federer held their first two serves to keep the scoreline level at 1-1. The American trails by 3-5 but Chung looks set to win this one. "He's incredibly impressive in his movement, reminds me obviously a lot of Novak", Federer said. But I'm not thinking about that any more.
0850 hrs IST: Some excellent groundstrokes by both the players as Sandgren attempts a comeback after a 15-shot rally. "She's hitting the ball so hard, the serve is also really fast, so I was just trying from the beginning, like I played the whole week, just going out there, playing my game and enjoying it".
Halep, the women's top seed, saw one of her top competitors bow out on Monday as well, with fourth seed Elina Svitolina falling in straight sets to Elise Mertens.