Rachal, a 6-5, 323-pounder in his third season, lay on the ground for several minutes but did not lose consciousness, Maiocco reported. He was taken to the locker room and was given an IV.
Maiocco said Rachal had just taken part in a pass-rushing drill when he collapsed. Niners coach Mike Singletary rushed over but said the player was already talking to trainer Jeff Ferguson.
"From the time I got over there, he was talking to Fergie right away," Singletary said.
Guard David Baas was already sidelined Tuesday after suffering a mild concussion during Monday's opening workout.