The influential 23-year-old winger, who returned for a second loan spell at Rovers late on in the winter transfer window has been affected by the problem, relating to a nerve injury, for a few weeks and will now be checked out back on the south coast.
Better news sees the potential return of midfielder John Bostock after missing the last four games with a groin issue.
Butler, speaking ahead of the League One trip to MK Dons on Saturday, said: “John is looking good and he will be training tomorrow (Friday) with us and it went well with the physio today.
“But one player who will be missing is Josh Sims, who has a slight recurrence with his tight glute.
“He has no power in his left leg, so we have sent him back to Southampton to get that checked over.
“We are waiting for Southampton to brief us and let us know what the injury actually is. Chats (Jon Chatfield - head physiotherapist) has done a lot of examinations and testing on him and he just feels the best way forward is for Southampton to check him out.
Meanwhile, Butler has confirmed that talks have started with some players whose contracts expire in June.
The Rovers chief, hoping to get the long-term position beyond this season and given licence to play for the future as he sees fit at the moment, said: “We have started contract talks and will speak to the players individually and put across what we would like to do next season going forward.
“Contact talks has already started and we will see where we go. I want a squad next season that is ready and settled.”
“It is important we stick together as we have a good core in our squad.”
Meanwhile, Rovers head of talent identification Adam Henshall is to leave the club later this Spring to join an unnamed top-flight club with his departure being an amicable one, according to the club.