The Red Sox, who lost the series opener, 10-8, are already down one second baseman, with Dustin Pedroia going back on the disabled list a couple of days ago with recurring discomfort in his right hamstring.
Fortunately, Holt's injury is much more of a short-term thing.
"He's improved today yet, at the recommendation of the medical staff, another day was needed," said Red Sox manager John Farrell. "Everything is pointing to him returning to the lineup tomorrow, and we felt like another day would do him well."
Weeks, the only backup infielder on the roster, got the start at second base on Tuesday night against the White Sox.
"Jemile was very impressive in Spring Training," said Farrell. "Moving all over the field, hitting from both sides of the plate. He's on short notice, obviously, with Brock's situation last night, but he jumps in, puts up two quality at-bats. He fought off a pitch with two strikes the other way for a bloop base hit."
Ian Browne is a reporter for MLB.com. Read his blog, Brownie Points, and follow him on Twitter @IanMBrowne. This story was not subject to the approval of Major League Baseball or its clubs.