The roster was announced Tuesday by U.S. captain Jim Courier. The event will be held on an indoor hard court April 5-7 in Boise, Idaho.
He already indicated his plan was to use those four players, who were on the team that beat Brazil in February. Querrey is ranked 20th, and Isner is 23rd. Mike and Bob Bryan have won 13 Grand Slam doubles titles.
The winner will face Italy or Canada in the semifinals in September.
Djokovic, a six-time Grand Slam singles champion, will be joined on Serbia's team by Viktor Troicki, Ilija Bozoljac and Nenad Zimonjic.