Soto was placed on the 10-day disabled list (retroactive to May 8) with right elbow inflammation.
Soto was scratched from Tuesday's game and then was put on the disabled list by the team for the second time this season. He was previously on the DL from April 12-22 for the same malady.
A very sharp pain in the back of his elbow started up again for Soto when he went to throw after stretching Tuesday. Surgery remains a possibility, the veteran catcher said.
"It's a possibility," said Soto, who is batting .190 with three home runs and nine RBIs. "Kind of waiting on what the best route is for us and see what the doctor can tell me about what's going on.
"Everything else I feel, it's there. But throwing, unfortunately, is what gets me sharply."
Smith replaced Soto behind the plate in April. He is hitting .377 with 15 RBIs for Charlotte, and was 1-for-11 with one RBI in his earlier stint with the White Sox this season.
"I love those guys down there [Charlotte] just as much as I love everybody up here," Smith said. "Good team chemistry down there and up here. It's an easy transition. I feel comfortable up here. It feels like I haven't missed a beat."
Putnam cleared to throw
White Sox right-hander Zach Putnam had a MRI Wednesday morning and was cleared to begin a throwing program as part of his injury rehab. Putnam, who has nine strikeouts with two hits and one run allowed over 8 2/3 innings this season, has been on the disabled list retroactive to April 23 with right elbow inflammation.
"Everything is good," Putnam said. "Looks like there has been some healing that's taken place, and I think everybody is comfortable with the progress being made.
"We aren't going to jump out there and get on the mound right away. Build up slow and hopefully be ready. We haven't discussed a specific timeline, but I'm hoping a week and a half, two weeks tops."
Putnam planned to start playing catch on Thursday and wasn't sure if he would need an injury rehab assignment. He went through extensive physical therapy in Michigan while the team was on its last road trip.
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.