US Open at a glance -- day 12
+ Del Potro in final after Nadal quits
+ Djokovic cruises past Nishikori in semi-final
+ Djokovic into 8th US final and 23rd at Slams
+ Bryan, Sock complete US Open/Wimbledon men's doubles sweep
-- Juan Martín Del Potro (ARG x3) bt Rafael Nadal (ESP x1) 7-6 (7/3), 6-2 -- retired
-- Novak Djokovic (SRB x6) bt Kei Nishikori (JPN x21) 6-3, 6-4, 6-2
Who's saying what
"I hate to retire but that was not a tennis match at the end. It was just one player playing, the other one staying on the other side of the court."
-- Rafael Nadal after retiring with a right knee injury in his semi-final against Juan Martin del Potro
"This year have been a fantastic year until this moment. I lost four matches. Two of them I had to retire. Negative thing is two of them have been in quarter-finals and semi-finals of a Grand Slam, close to fight for titles. That's frustrating."
-- Nadal who also had to retire in the Australian Open quarter-finals with a leg injury in January
"Everything is harder because I'm older."
-- Del Potro
"He's a gentle giant. He really is. He's very tall, has a big game, but at the same time he nurtures the right values in life. He cares about his family. He cares about his friends. He respects everyone."
-- Djokovic on Del Potro
"She's playing unbelievable tennis. She'll have a chance to beat Serena and I think she can stay with her. I hope she enjoys it."
-- Kei Nishikori, the 2014 men's runner-up, with advice for Japanese compatriot Naomi Osaka who meets Serena Williams in the women's final on Saturday.