Blake lost in the first round at Wimbledon last week. Fish reached the third round, Querrey the second.
This is the 12th time in the last 13 Davis Cup contests that McEnroe is using the same quartet of players.
The best-of-five quarterfinal will be July 10-12 on an indoor clay court in Porec, Croatia.
Croatia has beaten the U.S. both times the countries have played in Davis Cup -- the only country that has a winning record against the Americans.