I see Vucevic as a big upgrade over Garza. For the 12 games that Vucevic has been here:
Vucevic NRtg = +13.5 DRtg = 99.0
Garza NRtg = -16.5 DRtg = 121.8
I know it does not always look pretty with either, but Vucevic has been much better than Garza. This will hurt because Tatum will not have time to learn to play with Vucevic. Vuc has 12 games (really 11 games plus 2 minutes) with everyone else, but only 2 minutes with Tatum.