Drew Pomeranz surrendered six earned runs over five innings Sunday in a loss to the Diamondbacks.
Padres recalled RHP Leonel Campos from Triple-A El Paso.
Colin Rea is expected to rejoin the Padres' rotation this week.
Padres placed RHP Cesar Vargas on the 15-day disabled list with right elbow soreness.
MLB Network's Jon Heyman reports that the Padres "are fielding calls from a lot of teams" on James Shields but "nothing appears imminent" regarding a trade.
Padres optioned LHP Keith Hessler to Triple-A El Paso.
Padres activated LHP Matt Thornton from the 15-day disabled list.
Cesar Vargas got shelled on Saturday against the Diamondbacks, surrendering seven runs in just 1 2/3 innings.
The White Sox and Padres are reportedly engaged in trade talks surrounding James Shields.
Christian Friedrich blanked the Diamondbacks for seven innings on Friday to win as a starter for the first time since July 2012.
Yangervis Solarte hit a pair of homers to knock in four runs against the Diamondbacks on Friday.
Derek Norris went 2-for-3 with a homer, three RBI and two walks against the Diamondbacks on Friday.
Padres manager Andy Green said Friday that Tyson Ross (shoulder) could pick up a baseball within the next week.
Will Myers (forearm) has returned to the Padres starting lineup on Friday.
James Shields pitched respectably in Wednesday's no-decision against the Giants, surrendering two runs on five hits over six innings.