Tier 2 - Not quite untouchable, but likely not happening - Middleton, B. Lopez, and T. Antetokounmpo
In all likelihood, these three players will be Milwaukee Bucks past the trade deadline, but it's not as set in stone as the two others.
As frustrating of a season as it has been for Khris Middleton, he's still unlikely to be traded. The Bucks just handed him a new deal this past off-season, and his chemistry alongside Antetokounmpo does not need more rehashing. Even if some fans do not feel the same, Giannis has always talked about how much he enjoys playing alongside Middleton.
It would likely take a massive trade for the Bucks to consider dealing Middleton. Still, the likeliest scenario here is Milwaukee just holding onto Middleton and hoping he continues to work his way back to being his old self. He's shown glimpses, but he's still clearly aiming to try and find himself after an off-season knee procedure.
Next up is Brook Lopez, who also got a new deal in NBA free agency. While this year has been a bit of a new journey for the big man as he embraces new schemes under a new coach, it would be shocking to see the team move him. He's still a great fit alongside Antetokounmpo and this core, playing tough defense close to the hoop while providing scoring as well.
Again, the Bucks would have to be getting back a legitimate difference-maker if they were to move on from Lopez. Some fans think the Bucks could trade Lopez and run Antetokounmpo at center lineups, but that's not a full-time solution. Milwaukee still needs a starting center, and the odds of finding one who plays as well as Lopez on both ends is unlikely.
For obvious reasons, Thanasis Antetokounmpo is almost certainly not going anywhere. Fans can be irked by the Bucks using a roster spot on Thanasis, but at the end of the day, he's a good locker room presence, and if it keeps Giannis happy, that's a win.