MELBOURNE, Feb 15 (Reuters) - Quotes from day eight of the Australian Open tennis championships on Monday:
* "I am very motivated to win Grand Slams. The only thing that I said is I have never been obsessed. The ambition is important but if you have too much ambition you can be frustrated when you are not able to achieve all the things." Rafa Nadal, who is chasing a record 21st Grand Slam title.
* "We're not done yet. It's exciting to be in another quarter-final of a Grand Slam... but certainly not satisfied with where we're at the moment. We will keep chipping away and keep trying to do the right things to progress as far as we can." Ash Barty, who reached the quarter-finals for the third successive year.
* "I can't get more confident, it is my best result yet and I'm playing good tennis." Jessica Pegula after reaching her first Grand Slam quarter-final.
* "I think it's lack of focus, kind of distraction. To have the day like that is extremely disappointing." Elina Svitolina after losing to Pegula.
* "Sometimes you can maybe even not fight on the court but argue because we're competitors. After the match we are great friends. There is no rivalry in this part of competition." Daniil Medvedev on facing compatriot Andrey Rublev in the quarter-finals.
* "Unfortunately, there was only one winner and it was her, but to know that one of her top-two matches is unfortunate but also reassuring." Jennifer Brady on Naomi Osaka's remark that their U.S. Open 2020 semi-final was one of her top-two matches of all time.
* " ... it's amazing if it's never been (done) before and if it's the first time in history, then it's always something special." Rublev on three Russian men making it to a Grand Slam quarter-final for the first time in the Open era.
* "I got injured in the last match. I felt something on my ab. I thought that wasn't something really big but the next day I felt it was big. I spoke to the doctors and they told me I can get really worse, so it's not worth the try." Matteo Berrettini, when asked why he withdrew from his fourth-round match against Stefanos Tsitsipas.
Day eight highlights