H
When TAC becomes the voice of reason 
Nope that’s Komamura.
Even though I’ve never thought of this matchup, I am convinced Toshiro could win. Why? Hyoten Hyakkasō .
Even though Grimmjow will pressure him off the bat, he has ways of not ending up dead via his ice clone, running away if necessary (yes, this is what he did against Halibel to begin with) his bankai wings also provide decent protection.
If he is able to initiate it, Hyoten Hyakkaso finishes Grimmjow off.
Not even released Halibel was able to break out of that until Wonderweiss arrived, though you could argue it wasn’t strong enough to freeze her to the bone.
Toshiro evidently grew since the SS arc, a month passed since Aizen’s depature and he went from being relative to Luppi to being able to hang with Halibel.
The thing with Toshiro is that if you give him any sort of window he can muster up strong enough finishing attacks. His bankai’s versatility and potency is what made him keep up with Halibel who was otherwise stronger in terms of raw stats without a doubt.
This is precisely why Grimmjow doesn’t low diff him, Halibel wasn’t able to finish Toshiro off either and his ability to prep attacks like Hyoten Hyakkaso on the fly is deadly if he was able to initiate it.
With a far weaker attack than the Hyoten Hyakkasō at that.

Hitsugaya who is the weakest Captain has nothing to do here
Even though I’ve never thought of this matchup, I am convinced Toshiro could win. Why? Hyoten Hyakkasō .

If he is able to initiate it, Hyoten Hyakkaso finishes Grimmjow off.
Not even released Halibel was able to break out of that until Wonderweiss arrived, though you could argue it wasn’t strong enough to freeze her to the bone.
Toshiro evidently grew since the SS arc, a month passed since Aizen’s depature and he went from being relative to Luppi to being able to hang with Halibel.
The thing with Toshiro is that if you give him any sort of window he can muster up strong enough finishing attacks. His bankai’s versatility and potency is what made him keep up with Halibel who was otherwise stronger in terms of raw stats without a doubt.
This is precisely why Grimmjow doesn’t low diff him, Halibel wasn’t able to finish Toshiro off either and his ability to prep attacks like Hyoten Hyakkaso on the fly is deadly if he was able to initiate it.
With a far weaker attack than the Hyoten Hyakkasō at that.