The 30-year-old Headley can become a free agent after this season. He's hitting .229 with seven homers and 32 RBIs but has a .339 average since July 4. He was a Gold Glove winner two years ago, when he hit .286 with 31 homers and a National League-leading 115 RBIs.
As part of the deal, the Padres will pay $1 million of the $3,968,443 remaining of his $10,525,000 salary this year.
The 27-year-old Solarte was hitting .336 as of May 14 but just .180 since and was sent to Triple-A for a week this month. The 23-year-old DePaula was 6-5 with a 4.15 ERA in 17 starts and three relief appearances this year with Class A Tampa.