Francisco, who has already been on the disabled list twice for injuries, was put on the 15-day DL Monday because he is unavailable to pitch due to a mild case of pneumonia. Francisco, who first started feeling ill Saturday, wasn't even at the ballpark.
"He was available out of the bullpen, and then it just hit him too hard," manager Ron Washington said. "We didn't want him around the rest of those guys."
Francisco last pitched July 10, before the All-Star break. The move is retroactive to July 11, meaning the right-hander will be eligible to be reinstated Sunday.
Right-hander Willie Eyre was recalled from Triple-A Oklahoma City and was in the bullpen for Monday night's game against Boston.
The Rangers were also without All-Star outfielder Nelson Cruz, who was out for the second consecutive game with a broken right ring finger sustained diving into first base Saturday night after avoiding a tag. Washington said the team wasn't considering the DL for Cruz.
Cruz, a late scratch from Sunday's game after an X-ray revealed the fracture, said he was feeling better but that team trainer Jamie Reed told him to not to swing the bat Monday.
The Rangers said Francisco was home resting and taking medication.
Francisco (2-1, 2.28 ERA and 15 saves in 28 appearances) was out May 7-22 because of right biceps tendinitis and again June 4-20 with right shoulder tendinitis.
Even though the Rangers have been carrying an extended eight-man bullpen and had talked about adding another position player, they opted for another pitcher a day after five relievers combined for eight scoreless innings in a 5-3, 12-inning victory over Minnesota.
Eyre began the season on the DL with a right groin strain, then returned April 14 only to go back on the DL for the same injury nine days later. He allowed three earned runs in 5 1/3 innings (5.06 ERA) in four appearances.
At Oklahoma City, Eyre had a 2.29 ERA (five earned runs in 19 2/3 innings) in 10 games and last pitched Thursday.
Cruz, who is second in the American League with 23 home runs and finished second in the Home Run Derby at the All-Star game last week, said he is not worried about the finger lingering. It is the same injury Michael Young dealt with the final two months last season.
"He told me it was going to hurt," Cruz said. "You get jammed, it's going to hurt a lot. I've got to make sure I hit the ball well every time."
Young, who played 155 games last season despite also breaking another finger, said the hardest part is that the swelling will return at times.
"He asked me when did it start feeling better," Young said. "I remember New Year's Eve sitting at my house in California flexing my hand and saying, 'OK, it's starting to feel better now.'"