Gabriel is only 6' 9" and 205 lbs. While Queta is a bit slight, his size and preseason play made Gabriel expendable.
I would like to see another big Embid and/or perhaps Giannis defender - but Tatum's increased minutes at PF will be an upgrade over Grant who was a sub par rebounder.
True but whoever has to play SF in place of Tatum, while he is playing PF, will be a downgrade.
It will essentially work like this:
Tatum > PF (Grant?)
Brown < Tatum at SF
Holiday < Brown at SG
White < Holiday at PG
Porzingis = Porzingis at C
Brown isn’t much of a downgrade from Tatum at SF. Tatum is a big upgrade over Horford at PF. Al can play both the 4/5 off the bench. That’s an ideal situation. Holiday, White, Brown, Tatum, Porzingis is the best starting 5 in the NBA.
Brown is a pretty significant downgrade from Tatum. They are a different class of player. And Tatum has no business getting beaten on by bigger stronger players more frequently at PF.
And that certainly isn't clear cut as the best starting 5 in the sport. I'd probably take Denver (Murray, KCP, MPG, Gordon, Jokic) and Milwaukee (Lillard, Beasley, Middleton, Giannis, Lopez) over that. You could make a case for GS especially with a small Boston lineup (Paul, Curry, Klay, Wiggins, Dray), Phoenix (Beal, Booker, Okogie, Durant, Nurkic), and even Philly with an engaged Harden (Maxey, Harden, Harris, Tucker, Embiid), though Harden being engaged seems unlikely at this point.