Whether people get off his back or not doesn't matter. Mahaney is very likely the key to the season (the alternative is Nowell suddenly grasping the entire structure of the offense and grabs the starting spot).
The goal under Mahaney is to run through the full offense and use the entire shot clock if necessary -- with Mahaney kind of being an equally sharing possession.
Diara works as a change of pace, because he is more ball dominant and more direct leading to quicker strikes and the defense is caught off guard by the change. By the time the defense fully adjust, Diarra is heading back to the bench.
If Diarra is the main PG, UConn is playing in a limited offense -- and the defense isn't caught by the change. The team isn't able to get the most out of the interplay between the offensive strengths of the team (Karaban, McNeeley, and Ball). Instead Diara and Johnson become much more prominent in the offense.
I don't think there is a different gear for Diarra.