"The MRI was very similar to where it was this fall, which is very clean except for a bone spur on the back of his elbow causing him some of the discomfort," Daniels said.
Daniels said earlier in the day that surgery would likely mean the team would be without Kela until after the All-Star break.
The issue is left over from the end of last season, when he received an injection and responded well, Daniels said. Kela then successfully completed an offseason throwing program.
The right-hander appeared in seven of the Rangers' first 14 games, allowing five runs over 6 1/3 innings. His 12 strikeouts in relief were tied for sixth-most in the American League.
With the Rangers placing Kela on the 15-day disabled list, right-hander Phil Klein was recalled from Triple-A Round Rock.
Klein was in the bullpen on Opening Day and was sent down April 13 after seeing action in two games. He retired all nine hitters he faced with three strikeouts over three innings. He was sent to Round Rock to get regular work, though he never got into a game. He was scheduled to pitch on Friday.
Right-hander Tony Barnette will likely see most of the situations Kela saw in the late innings, manager Jeff Banister said.
"I think we have a group of guys we can maneuver around in the late innings," Banister said of a group that includes Barnette, Tom Wilhelmsen, Jake Diekman, Sam Dyson, Alex Claudio and closer Shawn Tolleson. "Barnette has thrown the ball very well."
• Daniels put a mid-May timetable for the return of Josh Hamilton, who was scheduled to travel to Arizona on Friday for extended spring training games before beginning a rehabilitation assignment in the Minors. Daniels said he believed catcher Chris Gimenez would return in early May. Gimenez is expected to go out to the Minors next week.
• Shin-Soo Choo, originally expected out four to six weeks with a calf strain, appears to be progressing ahead of schedule, Daniels said. "Choo is feeling great," Daniels said. "We haven't updated the timetable, but all signs have been very positive. He's got a chance to be on the early side of that."
• Outfielder Lewis Brinson, at Double-A Frisco, will miss at least a week with "instability" in his left shoulder. The team's first pick in the 2012 Draft, Brinson, 21, is hitting .267/.333/.467 in 45 at-bats. He is ranked as the Rangers' No. 2 prospect.