McDonald was selected by Los Angeles in the 11th round of the 2002 First-Year Player Draft and made his Major League debut with the Dodgers in 2008.
The left-handed hitting Lambo was rated by Baseball America as the Dodgers top prospect and best hitter for average in 2009. He began the 2010 season rated as best outfield prospect in the Los Angeles system; number seven overall. Lambo, 21, has spent the entire 2010 campaign with Double-A Chattanooga, where he hit .271 (49-for-181) with 11 doubles, four home runs and 25 RBI in 47 games.
Lambo was selected by the Dodgers in the fourth round of the 2007 First-Year Player Draft. He hit .343 in his first professional season in 2007 and was named to the mid- and post-season All-Star teams while playing with Great Lakes in the Midwest League in 2008.
McDonald is expected to join the Pirates at the Major League level while Lambo will report to Double-A Altoona.
The 27-year-old Martinez has made four appearances (one start) during three separate stints with San Francisco this season. He was most recently recalled on July 24 from Triple-A Fresno, where he went 5-3 with a 3.32 ERA (81.1ip/30er) in 14 games (13 starts). In his four games (one start) in the big leagues this season, Martinez has gone 0-1 with a 4.91 ERA (11.0ip/6er).
Martinez was selected by San Francisco in the 12th round of the 2005 First-Year Player Draft. Primarily used a starter during his professional career, he led the Eastern League with a 2.49 ERA in 2008 while posting a 10-10 record in 27 starts with Connecticut. Martinez made his big league debut with the Giants in 2009 and went 3-2 in nine games (five starts).
The left-handed hitting Bowker has spent a majority of the 2010 season with Triple-A Fresno, where he batted .310 (61- for-197) with 14 home runs and 36 RBI in 51 games. He also appeared in 41 games with the Giants and hit .207 (17-for- 82) with three homers and eight RBI.
Originally selected by San Francisco in the third round of the 2004 First-Year Player Draft, Bowker made his Major League debut with the Giants in 2008 and was one of the top rookies in the N.L. that season after batting .255 with 10 home runs and 43 RBI in 111 games.
Bowker, 27, was named to the Pacific Coast League mid-season and post-season All Star teams after hitting .342 (125-for- 366) with 22 doubles, 21 home runs and 83 RBI in 104 games with Fresno.
Martinez and Bowker are scheduled to report to Triple-A Indianapolis.