Bourjos tested his strained right hamstring with agility drills and ran wind sprints, but it tightened up on him.
"It didn't really respond well," Bourjos told the Los Angeles Times. "It's frustrating. It felt really good [Friday] morning. It stinks to sit here and watch, but that's where I'm at right now."
Trout was called up before the break to replace Bourjos, who the team thought would be up for just a couple of days around the All-Star break.
Bourjos will be eligible to be activated on July 23. Trout played in three games before the break, getting one hit in 10 plate appearances, with a walk and two runs scored. He is in the starting lineup against the A's and Brandon McCarthy for Friday night's game in Oakland.