Playing in Japan for the first time since 1997, the 54-year-old McEnroe took on Kei Nishikori, the 23-year-old Japanese star who rose to No. 11 in the world rankings this year.
Nishikori beat McEnroe 1-6, 6-4 and 10-7 in a tiebreak but the score hardly mattered as Sunday's match was about raising money for the Tohoku Tennis Association to help rebuild and rejuvenate tennis in the region devastated by the March, 11, 2011 disaster.
"Considering I just got in a few days ago, my body was moving pretty well," McEnroe said. "I was able to make some good shots but he took some mercy on me."
In addition to his competitive spirit, McEnroe showed flashes of his famous wit. "Is this a tennis match or a daycare centre, what the heck is going on here?" he shouted to a sold-out crowd of 10,000 when a crying baby interrupted a serve.
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."