Not necessarily considering he is Luffy big bro, it would be quite a shame for him to be weaker than his lil bro. This explain the whole flame emperor narrative even if am pretty confident Fujitora helped him considering the character.
Uncle Kizaru was ready to go bam when Sabo intervened. If it was a regular scenario, they could pull it off. But our light man was ready to solo the whole fleet, so he was at least semi-serious. Sabo'd die in such a scenario.