Ivo Karlovic and Ivan Dodig beat Tatsuma Ito and Yuichi Sugita 6-4, 6-4, 3-6, 6-3 Saturday to give Croatia a 2-1 lead over Japan in their first-round Davis Cup World Group series.
Karlovic made the most of his powerful serve, combining with Dodig for 24 aces.
Japan is returning to the World Group for the first time in 26 years after beating India 4-1 in a regional playoff in September. Croatia is seventh in the Davis Cup rankings, 10 places ahead of Japan.
Dodig is scheduled to play Nishikori in Sunday's reverse singles, while Karlovic will face Go Soeda.