The top five ranked American men are in the BB&T field.
Querrey, ranked No. 61, is the second-highest ranked American, ahead of Johnson (64). He and Johnson, who both grew up in Los Angeles, will team up in doubles to play Denis Istomin and Marinko Matosevic.
Monday was their first match as professionals, and Querrey won with 20 aces. In the first set, 68 percent of his first serves were in and he won 23 of those 24 points.
Querrey added the only service break in the second set to finish his pal. He has won seven ATP World Tour tournament titles since turning pro in 2006. Johnson is seeking his first championship.
"(The deco-turf hard court) suits my game. It takes a kick serve and rewards you with spin and jump, and rewards you with a fast serve and a slice," Querrey said. "It's not fun playing one of my best friends."
Young was uneasy playing close to home. He lives in midtown Atlanta, but that was no help Monday. Sela won easily despite double-faulting five times.
Young entered with a 2-1 career edge against Sela, including a 6-1, 2-6, 6-1, 6-0 win on clay at the French Open in the spring. Yet Young has lost in Atlanta's first round in 2011, '12 and '14, and did not survive qualifying in '13.
"It was pretty bad," he said. "I haven't had good results at all at home. Maybe there are too many people who I know around and things pulling me for tickets and a bunch of other stuff."
Isner, No. 2 seed Kevin Anderson and No. 4 seed Vasek Pospisil -- who earlier this month teamed with Sock to win the Wimbledon men's doubles titles while playing together for the first time -- will not play singles until Wednesday.
BB&T tournament director Eddie Gonzalez was critical of Monfils and Gasquet for withdrawing so late.
"They will be fined heavily by the (United States Tennis Association)," Gonzalez said. "We can't build a whole campaign and then have them disappoint our Atlanta fan base."