So at the end of last season, we had a squad of 27 players which included 4 players that were acquired during the January transfer window due to the fact that Bremer, Cabal and Milik were not available - these were: Veiga, Kelly, Costa and Muani - and they offloaded Danilo in January - meaning we started the season last year with 24 players with Mbangula, Savona and Rouhi promoted from NextGen - meaning we had 21 excluding those. Our current squad (including Milik & Rouhi) is 25 by my count.
If 3421 is the formation of choice, then the way I look at it, we only have 4 dangerous players for the front three including Vlahovic - 5 if you include Nico (who I don't consider dangerous). I wouldn't rule out Muani but given that Vlahovic stays - then surely, Tudor would need to re-think the formation unless Muani will be used frequently as a wide player.
At the bare minimum we need at least one attacking player because if one of Yildiz or Conceicao is not available, our attack is lacking a lot. Weah, Muani and Mbangula were pacy wide choices that are gone now.