Simon cut last week by Pirates
Simon was released by Pittsburgh last Saturday. He hit just .194 with three home runs and 14 RBI in 61 games with the Pirates.
Simon, 29, has a career batting average of .285 in 506 games. He spent most of last season with the Pirates before he was traded to the Chicago Cubs. He re-signed with the Pirates in February, a one-year deal worth $800,000 with a club option for 2005.
Simon's mother died this past spring, and he injured his hamstring early in the season. The injury nagged him for several weeks.
His time with the Pirates might be best remembered for an incident in July 2003 at Miller Park in Milwaukee, when he struck one of the Brewers' racing sausages with his bat during a game. Simon was cited for disorderly conduct, posting $432 bond which he later forfeited, ending the case.
Witasick, who has not pitched since recording his first save of the season on Aug. 13, is 0-1 with a 3.26 ERA in 41 appearances this year. The 32-year-old veteran owns a 29-36 career record with four saves and a 4.73 ERA in 286 games, including 56 starts, with Oakland, Kansas City, the New York Yankees, San Francisco and San Diego.
To replace Witasick on the roster, the Padres purchased the contract of right-hander Steve Watkins from Triple-A Portland.
Watkins, 26, combined to go 9-6 with a 3.37 ERA in 32 games, including 16 starts, with Portland and Double-A Mobile this season. He owns a 38-38 career mark in 183 games in the minor leagues.
Larson was to join the Louisville Bats in time for Thursday night's game at Indianapolis.
Larson is hitting .212 with three home runs and 14 RBI in 40 games this season.
Perez, a former Gold Glove winner with the Rockies in 2000, will be assigned to Triple-A Iowa.
He started the season with San Francisco but was released Aug. 13. He batted .232 with 15 extra-base hits and 33 RBI in 120 games.
Perez was originally signed by Colorado in 1992 and spent eight-plus seasons with the organization. He played in all 162 games in 1998 while batting .287 with 71 RBI.
A team spokesman said the exam was a precautionary measure. Wells is 5-7 with a 4.50 ERA in 23 starts.
John Van Benschoten replaced Wells in the rotation on Wednesday, then was optioned back to Triple-A Nashville after the game.
The Pirates also recalled right-hander Ian Snell from Double-A Altoona. Snell was the Pirates' minor league pitcher of the year in 2003.
Information from The Associated Press and SportsTicker was used in this report.