Newspapers noted Greb as being hurt in certain fights so its not like his chin couldn't be penetrated. Hagler didn't know when to box. He had no problem being aggressive. I doubt that Greb would be boxing Hagler judging from eyewitness accounts I have read. Tunney wasn't a volume puncher either but he managed to beat Greb a few times. I think its Greb's punch count is massively overrated. Sure, he threw a lot of punches but its not like he was a non stop punching machine.
Greg might have had Ali type of durability. Hurt a few times, but he recovered nicely. With the amount of fight he had, his action style, plus those lighter gloves his boxing era used, the only conclusion is his chin was excellent. Greb was a grinder, capable of outworking guys late. News reads tell me this. I think Tunney could be a volume puncher if needed. Greg beat Tunney who Tunney was a bit pre-prime ( Tunney only official loss ).
Of course. I don't want to make it sound like I think Greb didn't have a terrific chin, he just wasn't immune to pain. From the film I have seen of Tunney I wouldn't say he was a high volume puncher. Very precise with the punches he did throw and didn't waste any.
I favour Hagler for me he had all the tools. Now Hagler vs Greb is definitely a fight i would have paid good money to see, no quarter sought or given by either fighter. I think it would be Hagler vs Hearns round one reprise, for each and every round Hagler and Greb fought.
A case could be made for Greb winning 4 out of the 5 fights. Only once did Gene win decisively, the others were close calls with 1 having even Gene surprised he won
I wish we had the fights on film. Would be very interesting to watch and compare to newspaper accounts.