Jenks, who is still waiting for a second kidney stone to pass, was at the ballpark Tuesday night against the Angels but left before the start of the game, headed to Rush University Medical Center.
"We sent him to the hospital," Guillen said of the White Sox closer. "Hopefully, the physical problem is out in the next couple days. Hopefully, today. We'll see what happens. We've been waiting for that for the week and he's not getting better. That's why we sent him to the hospital."
Guillen estimated that Jenks could be back as soon as Thursday for the series finale against the Angels, although Jenks could have a procedure done to break up the remaining kidney stone. In the meantime, Guillen said he would use a closer-by-committee approach, involving Matt Thornton, Scott Linebrink and Octavio Dotel.
Ramirez suffered a sprained right ankle while trying to break up a double play on July 29 in a 3-2 loss against the Twins. Before Tuesday's game, Ramirez took ground balls in the infield but did not look particularly comfortable doing so, according to Guillen.
"I think [Ramirez] is a little scared moving around," Guillen said. "He feels a lot better. If we need him in an emergency situation, he will play today. Hopefully, tomorrow. I'm not going to put a set table for tomorrow. Hopefully, he'll be ready in the next couple of days. I'm not thinking he'll be ready tomorrow anyway."
Guillen also said that his starting staff would continue to pitch on regular rest while he waits to see who will take over as the White Sox eventual fifth starter. Left-hander John Danks will throw Thursday on four days' rest thanks to Monday's off-day. Chicago traded its previous fifth starter, Clayton Richard, to San Diego in a non-waiver Trade Deadline deal to acquire Jake Peavy.
The White Sox could recall Carlos Torres from Triple-A Charlotte to fill the fifth-starter spot. Torres threw six innings of three-run ball in his Major League debut on July 22 against the Rays. The team's other option would be to use reliever D.J. Carrasco. Carrasco made his first start in three years on July 31 against the Yankees, allowing five runs on nine hits in four innings of work.
"As long as I have one on the mound," Guillen said, "that's all I care."
Jesse Temple is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.