"We'll try to get him back on his feet again," manager Rick Renteria said. "It's tough for me to have him here. The window right now is just right" for him to go to the Minors.
Lake was told he would be back with the big league team when rosters expand on Sept. 1.
"Any time you have someone who has been with you as long as he's been with us, and you send him down late, it's obviously disappointing," Renteria said, "but I think he understands he'll get some at-bats and he knows he'll be back."
Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.