Simoes, who arrived at the club in January for the rest of the season on loan, has not been in Rovers' matchday squad for the past five matches and despite Rovers having injuries going into Tuesday night's game at Crewe, he was again not involved.
Butler says that at the minute, Simoes is a casualty of EFL rules regarding loan players, with clubs allowed to name a maximum of five loan players on a team sheet for any individual match.
Rovers currently have eight loan players on their books, although one in Tyreece John-Jules is on the injured list and receiving treatment at parent club Arsenal.
Alongside him and Simoes, the other loanees at the club are Taylor Richards, Matt Smith, Josh Sims, Scott Robertson and Ellery Balcombe, with Simoes effectively the odd man out regarding those who are currently available.
Butler said: “Obviously, at the moment, we have got a lot of loans and it is fitting the loans into it.
“If he was not a loan player, he would be in the squad, but it is just the sheer number of loans we have got at the moment that means it is difficult to get him in.
“But I have spoken to Elliot and once he gets a chance, he has got to prove that he can rise to the challenge and take the opportunity."
It is proving to be the toughest of season for Simoes, with the former FC United of Manchester player was frozen out under Barnsley head coach Valerien Ismael in the autumn after featuring just twice in the early weeks of the Frenchman's tenure.
His final game arrived in the 3-0 loss at Cardiff City on November 3 when the Reds chief brought him off after forty minutes, with Ismael subsequently firing a broadside in the direction of the 21-year-old when he questioned his 'intensity' and seriousness.'
Simoes admitted that his exile from the first-team picture at Barnsley represented the hardest time of his professional career, with Ismael having urged him to use his time at the Keepmoat Stadium to improve his mentality.
Speaking earlier this year about a testing time in his career, he acknowledged: “One hundred per cent. You hear about things that will always happen in your career, but I did not think it was going to happen to me that early, as I was doing quite well and suddenly, I just went from playing and scoring this season to not being involved in the squad - literally in the space of a week.
“So in a mental way, it was quite hard for me and Doncaster really kind of got me back.
“I felt like I was doing okay (at Barnsley) and had scored this season and was playing well. We were not doing the best in the league, but the Championship can change in a few days and we had faith we could change it.
"I felt I was doing well and my team-mates felt that. But then the manager had different plans.
"At that point, I felt like I was mentally low and down with football and those moments were really hard for me. The club knew and the players knew and my family also knew that.
"But once I got the news I could go on loan, I got ready mentally again to get back into football and it made me quite happy.”