Coulibaly only joined Rangers in the summer on loan from Angers, and he made a very positive start at Ibrox.
However, in recent weeks, the midfielder’s form has dipped slightly, leaving questions being asked of the 22-year-old.
Indeed, during Rangers’ match against Spartak last night, McCoist felt that Coulibaly was holding on to the ball for far too long.
He said: “The problem with Coulibaly, for me, is that he passes it when he wants, and not when his teammates want it.
“He needs to pass the ball quicker and earlier, he is taking too many touches.”
Rangers were beaten 4-3 in Russia yesterday, with Steven Gerrard’s side slipping to their first European defeat.
Rangers had to lead three times in the first-half, but they just could not hold on to their advantage.
The Ibrox side continuously made mistakes at the back to allow Spartak to pick up the three points.
Rangers’ Europa League group is now tightly congested, and Gerrard’s side will be under pressure to get back to winning ways next time they are back in European action.