‘A champion’s champion’: Nadal and other tennis stars react to Roger Federer retirement

• Swiss star announces retirement from tennis after stellar career
• In pictures: Federer's remarkable tennis career

The tributes poured in quickly on Thursday when Roger Federer announced his retirement from tennis after a career than lasted more than two decades and brought him 103 singles titles.

Federer's rivalry with Rafael Nadal has been a defining part of tennis this century, and the Spaniard expressed his regret they will not meet again in a grand slam final.