Atlanta has won eight of 10. Johan Camargo had a two-run double off the left field wall in the fourth to begin the scoring, and Atlanta added an unearned run in the eighth.
Newcomb (1-2) made his major league debut June 10 and has a 1.48 ERA through four starts.
He issued one walk Tuesday and allowed six hits. The 24-year-old left-hander was a touted minor leaguer when Atlanta acquired him from the Los Angeles Angels in 2015 for Gold Glove shortstop Andrelton Simmons.
Padres starter Jhoulys Chacin (6-7) retired his final 10 batters, working seven innings for the third time in the past four starts.
Jim Johnson recorded his 16th save.
