The first game is slated for 12:05 p.m. ET with a 6:05 p.m. first pitch scheduled for Game 2 in the split-admission twinbill.
Phillies right-hander Nick Pivetta will face Tyson Ross in the first game, and San Diego's Luis Perdomo will match up against Vince Velasquez in the second game.
The teams are hoping to avoid more rainy weather Sunday during San Diego's only scheduled trip to Citizens Bank Park this season. The Phillies took the first game of the three-game set with an 11-5 victory Friday night.
Philadelphia (54-42) is still a half-game ahead of the Atlanta Braves for first place in the National League East. Playing against the Nationals in Washington, D.C., the Braves were also rained out Saturday.
Pivetta (6-7 4.58 ERA) will try to help the home team stay in first and capture a series victory in the first game. The second-year major leaguer, who has a 4.50 ERA in two career starts against San Diego, experienced a shaky end to the first half of the season, posting a 9.00 ERA in his last three starts.
Ross (5-8, 4.32), meanwhile, could be making one of his final starts in a San Diego uniform. The right-hander, who is on a one-year contract, could be dealt to a contender as the Padres continue to sell before the July 31 trade deadline after dealing Brad Hand to the Cleveland Indians on Thursday.
The 31-year-old had a 3.32 ERA at the end of June but got off to a tough start in July. Ross combined to give up 15 earned runs in his first two starts this month before getting back in a groove before the All-Star break. Ross gave up two runs and three hits in 6 1/3 innings against the Los Angeles Dodgers in his last start on July 12.
Ross is 0-2 with a 4.76 ERA and 1.118 WHIP in five career appearances against the Phillies.
In the nightcap, Velasquez will be facing the Padres for the second time in his career. The first start was rather memorable.
Velasquez (5-8, 4.39) struck out 16 batters and threw a complete-game shutout against the Padres on April 14, 2016, in Philadelphia. The start featured only three hits and no walks, and it came in Velasquez's second outing with the Phillies.
Velasquez has not quite been able to match that success in 2018, but he has been sharp in each of his last five starts.
Velasquez has a 3.00 ERA in his last five games, which have come on both sides of a brief stint on the disabled list for a bruised forearm. He has allowed just 13 hits and struck out 27 batters during that span (27 innings).
The 26-year-old held the New York Mets scoreless for six innings, giving up only two hits and a walk on 85 pitches in his final start of the first half on July 11. It was Velasquez's first start since the injury.
"He was simply dominant," Phillies manager Gabe Kapler told reporters about Velasquez after the start. "There was not a lot of hard contact off Vinny, and he did as good a job as could possibly be asked of him coming off 10 days down."
Perdomo (1-4, 7.55) has spent time in the majors and Triple-A this season. He has three starts since rejoining the San Diego rotation earlier this month, posting a 6.88 ERA and a 1.765 WHIP in those appearances.
With Triple-A, he is 6-2 with a 3.10 ERA in 11 starts.