I continue to submit that Vogt lost us as many games (or more) than he won for us, even early in the season.
He was at least arguably doing more good than harm when he was scoring. Now he is borderline unplayable with his defense and lack of scoring.
The difference between the defensive abilities of Vogt and Diarra is huge. When Vogt is in we double Vogt's man, collapse more guys to the paint to provide help and have trouble stopping the drive. With Diarra in we don't need to double, Diarra cuts off drives before they even start and provides good help defense in the paint (though he is still learning when to go for the block and when he should back-off and box-out).
Diarra is averaging only 1.3 fewer points in conference than Vogt, rebounds better, defends better and can stretch the floor by shooting threes. Yes, he is more mistake prone, but we've seen that if he's given time and a chance to play through the mistakes, he is a better player than Vogt (and has way more potential).