But Federer just pauses and, taking a deep breath, serves a blistering ace.
The 17-year-old, realizing he's beaten, simply shrugs.
"He's the best tennis player ever," he says. "I am just lucky we played ping-pong."
Jirata says he will never forget taking two points from Federer in an impromptu game of table tennis at a school the tennis ace funds in the poor country.
For Federer, this week's visit to Ethiopia was one that moved him to tears. More + images...