Monday's match lasted 94 minutes, but was a full three-set battle that saw Lopez recover from a slow start to triumph.
The sixth seeded Spaniard had his service broken twice and fell behind in the first set, but he would not be broken on his service for the remainder of the match as he found form and put away Querrey.
To help his cause, Querrey went backwards during a contest that saw him lose five games on his service and commit four double faults.
In earlier Delray action, Adrian Mannarino topped Jack Sock in straight sets 6-4 6-2.
Mannarino had fallen to the American Sock in their two other matchups this season but broke through in a big way.
Despite Sock's seven aces, the Frenchman was able to pounce on Sock's second serve attempts and capitalize.
The other results filled out the four qualifying spots in the 32-player field that includes No. 1 seed Tommy Haas of Germany.
(Writing by Jahmal Corner in Los Angeles; editing by Amlan Chakraborty)
