In 2013, Thornhill's son Milos Raonic rode his rocket serve to become the ATP's 10th ranked men's singles player. No Canadian man ever ranked higher. Raonic ranked 11th at season's end.
Two victories supported Raonic's rise. He won the Pacific Coast Championships in February, defeating Tommy Haas in straight sets 6-4, 6-3. In September, Raonic beat Tomas Berdych 7-6(4), 6-3 at the Thailand Open. Both victories were on hard courts. Raonic also reached the finals at both the Canadian Open, falling to Rafael Nadal 6-2, 6-2, and at the Japan Open, where he lost to Juan Martin del Potro 7-6(5), 7-5.
2013 also saw Raonic lead an unseeded Canadian team into the Davis Cup World Group semi-finals. Canada's tournament began in Vancouver, where Canada beat the top-ranked team from Spain before a rowdy, supportive crowd. Canada eventually lost to 4th-seeded Serbia, anchored by world #1 Novak Djokovic, 3-2 on a slow clay court in Belgrade. This was only the 6th time Canada reached the World Group, and represents the nation's furthest advance in Davis Cup play. A century earlier, in 1913, Canadians reached the semifinal when the tournament was known as the International Lawn Tennis Challenge.