That's when the A's made a late call to corner infielder Max Muncy, who joined the club Saturday morning, and decided to put Zobrist on the 15-day disabled list.
"I wasn't getting out of the box well at all," said Zobrist, batting .240 in 14 games. "And frankly, the worst thing out of it was just trying to swing. When I swung right-handed, specifically, it put a lot of pressure on that front knee, the left knee.
"I just didn't feel like I could be the player that this team needs me to be in the condition that I was trying to play in. So gotta get it cleaned up and get back out here as soon as possible."
A surgery date will be set soon.
"This is the thing to do, to get him back sooner than later, and this way, once he rehabs and he's healthy again, he won't have this weighing on him," said A's manager Bob Melvin. "We brought him in here for a reason, to be a significant factor for us. But depending on the timetable, we're going to get him back for most of the season. These are the things you have to deal with over the course of the season."
With Zobrist out of the mix for at least another month, Eric Sogard is expected to assume everyday second-base duties. In the batting order, catcher Stephen Vogt will continue to draw starts in the third hole, Zobrist's normal home.
Vogt entered Saturday batting .373 with a team-leading four home runs and 14 RBIs.
"Certainly the way he's swinging now," said Melvin. "We want our best hitters in the middle of the order. Zo was the guy for the three spot. Since he's been out, Stephen's done a nice job with it. As long as he's swinging the bat well, I can see him there."
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, and follow her on Twitter @JaneMLB. This story was not subject to the approval of Major League Baseball or its clubs.