Martinez has been thrown into Terry Francona's lineup at the No. 3 spot and will strap on the big mitt as he's taking first base duties for Saturday night's game against the O's.
Kevin Youkilis has slid across the diamond and will play the hot corner and bat cleanup while David Ortiz remains the designated hitter and will bat fifth.
Martinez will be making his Red Sox debut against Os' hurler David Hernandez. V-Mart is a .290 hitter in 27 career games against the Orioles but has yet to face the rookie Hernandez, who is 3-2 with a 3.20 ERA.
Lowell has been one of Boston's hottest hitters as of late, riding a 10-game hitting streak since returning to the club following a brief stint on the 15-day disabled list. Since his return on July 17, Lowell has gone 14-for-36 (.389) with nine RBIs, four doubles, one home run and four runs scored. He has struck out just twice in that span and raised his season average from .285 to .295.
Boston's other addition, first baseman Casey Kotchman, is in the clubhouse but not starting. To make room for both Kotchman and Martinez, the Red Sox have reportedly optioned pitcher Marcus McBeth to Triple-A Pawtucket and placed catcher George Kottaras on the disabled list.