Rafeal Nadal and Roger Federer are partners of the Laver Cup tournament as they represented Europe in the inaugural Competition.
The 19-time Grand Slam champion Federer lost the opening set to Australian Kyrgios as Team World looked to force a deciding doubles match at the event in Prague.
Nadal was seen talking to Federer after the first set and the Swiss legend went on to complete an impressive comeback, eventually winning a tense tie break.
Asked by Sky Sports what advice he gave Federer, US Open champion Nadal said: ‘Just to be a bit more aggressive.
‘He is playing great, and controlling the points from the base line.