He will be in uniform today when the Padres play the finale of a three-game series at 12:35 p.m. at San Francisco.
Originally selected by San Diego in the fifth-round of the 1999 First-Year Player Draft, Thompson has a career Major League record of 4-6 with a 5.28 ERA (60 ER/102.1 IP), 40 strikeouts and 33 walks in 24 games (16 starts).
Chase Headley's contract was purchased from San Antonio on June 15. In seven games, including five starts, the 23-year-old third baseman was 3-for-17 with one double, one run and two walks for the Padres.
Headley has hit .357 (81-for-227) with 21 doubles, three triples, 13 homers, 42 RBI and 45 runs scored in 62 games for San Antonio this season. When his contract was purchased, the switch-hitter was leading the Texas League in batting average, hits, on-base percentage (.433), slugging percentage (.648) and extra-base hits (37). He was named the Padres Minor League Player of the Month for April after batting .360 (31-for-86) in 24 games for the Missions during the month.