I wanted them to find a successor last year. The Brogdon thing fell in their laps and I'm sure they felt they couldn't turn it down, but the 2023 first-rounder was one of their few expendable and tradeable assets. I don't really understand this idea that Gallinari was supposed to help. Sure, he's 6'10'' but you're just going to forget about all the stuff Horford does on defense and the screens he sets on offense? Gallinari seems more like an offensive specialist to me. Horford didn't even play the 4 a lot this year, he was primarily a center. If you put Gallinari at center you're basically going all offense, 5-out, gimmick lineup, so that doesn't sound like a feasible long-term option either.
Regardless of whether they end up getting a strict 4 or a 5 or a hybrid of both, they just need more playable guys with size to hold up in the playoffs. In the battle of attrition, Horford couldn't hold up, especially with the way they kept losing games and allowing series to go 6 and 7 games and only one day of rest in between. They need someone who can do all the dirty work and grab rebounds and capably defend the best players when switched onto. It should be somebody who cares little about numbers or point totals and can show the Js and the other passive guys on this roster a little fire and energy.
All the best teams have these kinds of guys, versatile big wings or PFs like Aaron Gordon, Andre Iguodala, Draymond Green, etc. I don't think Tatum can do it because he's already our best offensive player and his body is top heavy. He gets flustered mixing it up inside because ultimately he doesn't have the hips to create enough leverage. How many times have you seen him struggle to get enough separation just to receive an entry pass? He's 6'9'' but he's off balance because he doesn't have that lower power base to establish himself. I sometimes wonder if he should just go back to being lighter like Durant, regaining some of his burst and focusing on perfecting the outside shot.
The problem is these guys are rare and usually cost money unless you get a lesser version of them (e.g. PJ Tucker). You can show that you're a title contender and maybe some vet goes there for cheap, but it's not like the Celtics are a sure thing right now. They can't be paying three guards 17-22 million and not having any frontcourt depth, it's just bad balance. Their backup guards should be cheaper players that they developed, like Austin Reeves, Christian Braun, or Immanuel Quickley. Or, you just go bargain hunting with the mid-level with vets like Donte DiVincenzo or Bruce Brown last year.
Obviously it's tough to find taller two-way players as opposed to scoring guards which are relatively common. Maybe you don't even successfully get the perfect guy this offseason. However, long term I don't think you win a title without a true Horford replacement either at the 4 or 5. They didn't get one last year, hopefully they find one this year. The chances that it's someone as good as Horford was is miniscule unless you deal a major asset though.