Major takeaways from day seven at US Open 2019

Novak Djokovic's US Open title defence came unstuck when a nagging shoulder injury forced him to retire from his fourth-round match against Stan Wawrinka. 

Wawrinka was leading 6-4, 7-5, 2-1 when Djokovic decided he could not continue. 

Roger Federer, chasing his 21st Grand Slam title, advanced to the US Open quarter-finals on Sunday by routing Belgian 15th seed David Goffin 6-2, 6-2, 6-0. 

Federer, a five-time champion at Flushing Meadows, advanced to the US Open quarter-finals for the 13th time by routing Belgian 15th seed David Goffin 6-2, 6-2, 6-0 in only 79 minutes.

Serena eager to return after lockdown break

Roland Garros champion Ashleigh Barty crashed out of the US Open in the last 16 after a wild display against Wang Qiang. 

"It's a tough day at the office today. But it has been a year where we've hit our goals," Barty said.

Johanna Konta avenged her Rome final loss to Pliskova in May, beating the Czech third seed for just the second time in eight tries, 6-7 (1/7), 6-3, 7-5.

The British 16th seed has raised her game at the Slams this season, and is enjoying her best run at Flushing Meadows, having twice reached the fourth round.

Grigor Dimitrov, plagued by injury this season, qualified for his first Grand Slam quarter-final since the 2018 Australian Open after a straight-sets defeat of Australian Alex de Minaur.

The Bulgarian then revealed his fondness for the Backstreet Boys, having recently uploaded footage of him singing along at concert.

"Every night I'm vibing to those guys. It's great I love music, I love being in a great atmopshere. Let's keep the song going," he said following his win on Court 4.

Elina Svitolina and Johanna Konta bumped the number of active women's players to have reached quarter-finals of all four Grand Slams to 15.

Fifth seed Svitolina's best Slam performance came during her run to Wimbledon semi-finals in July, while Konta has made the last four everywhere but in New York. 

Serena Williams is one victory shy of 100 at the US Open after brushing Petra Martic aside 6-3, 6-4.

The American is chasing a seventh Flushing Meadows crown and only trails Chris Evert (101) for most wins at the year's final Grand Slam