Number two seed Murray defeated Kyrgios 7-5, 6-1, 6-4 in a match where the Australian played well initially, but was not the same player for the remaining two sets, where he did not seem as committed to the match as it went on. "The rest of the match was pretty pathetic", Kyrgios said. "I couldn't compete today", said Nishikori. "I have to go out there believing".
On the loss at the US Open, "I lost to him at the US Open (in) four sets, I played him in Hopman Cup, beat him there".
The 22-year-old was ranked 90th in January but is now up to 30 and will climb further after reaching the fourth round of a slam for the first time.
Kyrgios said: "We joke a lot".
"So, yeah, I'm just here to do the best I can".
"But Andy, I don't know, it's different", said Kyrgios.
"Like, one week I'm pretty motivated to train and play".
"Every year I play here [the pressure's] the same. He's just snapped", McEnroe told the BBC during the second set. "One week I'll just not do anything".
"I'm not meaning to be rude or disrespectful at all", he said after booking a centre-court showstopper with Andy Murray on Monday.
"It's not just the mental side, he needs to work harder at his game".
Yesterday, Federer drew level with Martina Navratilova on a record 306 grand slam singles match wins.
"I'm hoping he sees the writing on the wall before this becomes chronic, irreparable, because to me it's getting to that point".
'I still think he is going to win slams, but not in the way he played there'.
For much of Monday's first set on a packed Centre Court, Murray played second fiddle to 15th seed Kyrgios, who thudded down serves at close to 140 miles per hour that the world number two struggled to reach let alone control.
This was certainly not the Kyrgios who burst onto the tennis scene so spectacularly two years ago with victory over Rafael Nadal on the same court.
There were times when Murray seemingly had Kyrgios on a string as he pulled the world No. 18 into the net with deft drop shots and then sent him scampering back to retrieve killing lobs.
Kyrgios has got a big serve and massive forehand which he could do damage to Murray but the Brit enjoys returning against big servers.
"This is not doing our sport any good".
"There's not one way of tackling it. But if you want to continue to get better, then you speak and listen to as many people as you can, and take on board the things you think will help you".
'It was all working and was a great performance, but that was because he wasn't feeling a lot of pressure from Kyrgios.
"I think this would be an important time for his parents to look him the eye and people like Lleyton Hewitt, these are the people who have got to force him to look in the mirror".
Kyrgios let fly at his courtside box, including his father and agent, for not offering enough vocal support during his third-round win over Feliciano Lopez.
"Kyrgios has got to take responsibility for what is going on".
"It's obviously been tough", said Kyrgios.