With the score tied 6-6 in the tiebreak, McEnroe gave an assessment of his opponent's condition "looks like he's runnin' out of gas" and made a few of his trademark rants over close calls and the occasional thrown racket.
McEnroe said he was more than happy to visit Japan and help out the people on the country's northeastern coast.
"It's good to try to help people through a difficult time," McEnroe said. "Unfortunately, disasters like this seem to be happening more and more these days."
Nishikori, who has helped contribute to a rejuvenation of tennis in Japan in recent years, said he was impressed with the play of the winner of seven grand slam titles.
"He played a lot better than I expected," Nishikori said. "I was surprised. His shots were very good. I really enjoyed playing against him and it was a great experience."