Rodriguez suffered a subluxation of his right knee on Feb. 27 and started the season on the disabled list. He could make another rehab start before rejoining the Red Sox.
Kelly, who is recovering from a right shoulder impingement, looked strong in a bullpen session and should be able to start a Minor League rehab assignment for Pawtucket on Friday. He will make at least two starts for Pawtucket.
Lefty Henry Owens would be the top candidate to come out of the rotation when Rodriguez or Kelly returns. It is less certain who else would be squeezed out.
"We've got a ways to go before we have to make a decision," Red Sox manager John Farrell said. "Somehow these things sort themselves out a little bit. I don't have that crystal ball yet that shows what another 10-14 days says right now. We'll take a look at where guys are that are in the rotation right now, and what is best for the Red Sox. That's the best I can tell you right now."
Ian Browne has covered the Red Sox for MLB.com since 2002. This story was not subject to the approval of Major League Baseball or its clubs.