Feldman threw his first complete game and had a personal-best 12 strikeouts. He walked only one and also drove in a run with a double.
After compiling a 39-44 record in his eight seasons with Texas, Feldman joined the Cubs this season and gave up 22 hits in 20.2 innings during his first four starts.
Although he gave up solo homers in the eighth and ninth, Feldman (2-3) was allowed to stay in the game and eventually threw 112 pitches.
Feldman doubled in a run in the second and Dioner Navarro had a two-run double in the third that gave the Cubs a 4-0 lead.
Andrew Cashner (1-2) surrendered five runs on six hits in four innings to take the loss. San Diego suffered only its second setback in seven games. Chicago has won five out of seven.