A MRI taken for precautionary measures confirmed the "mild strain in a bad spot," according to Robertson.
"I was hopeful it was going to fix itself and I would be able to pitch in the upcoming games," said Robertson, who has 23 saves, 27 games finished and a 3.22 ERA this season. "It's making it tough for me to pitch right now, because I can't move that well.
"Doctors are saying a couple of days. So I'm thinking right after the All-Star break I'll be ready to roll."
Robertson's status was not discussed prior to Saturday's 5-4 victory for the White Sox over the Braves, with the focus of Ventura's pregame media session falling upon Carlos Rodon's trip to the disabled list. So it seemed a bit strange when setup man Nate Jones didn't start the eighth but came into the game after Matt Albers had given up a Chase d'Arnaud double and intentionally walked Freddie Freeman with two outs.
Jones struck out Nick Markakis to end that frame, but picked up an even bigger strikeout of Erick Aybar with runners on second and third and one out in the ninth. D'Arnaud grounded out with the bases loaded to end the game, after the White Sox intentionally walked Ender Inciarte.
"Nate had it covered. He got the job done. He did a great job," said Robertson of Jones' third save. "Obviously I would have loved to pitch in this series, but it's a tough break for me. Guys are doing their best picking up the slack."
"He was unavailable today, as far as just thinking it would get worse if you put him out there," Ventura said. "Everybody was kind of aware where they were going to be as far as coming in and matching up. They did a good job."
Scott Merkin has covered the White Sox for MLB.com since 2003. Read his blog, Merk's Works, follow him on Twitter @scottmerkin, on Facebook and listen to his podcast. This story was not subject to the approval of Major League Baseball or its clubs.