Kizaru is always associated with right-hands or top level crew members;
- Kizaru vs. Arlong (when Arlong was with Fisher Tiger)
- Kizaru vs. Pre-TS Zoro
- Kizaru vs. Rayleigh
- Kizaru vs. Marco
- Kizaru vs. Benn Beckman
And Akainu + Kizaru joined the Marines in the same year, and they were always portrayed as Marine duo, at least they are much closer than Aokiji was to Akainu or to Kizaru.
So if Kizaru always takes on the top crew members or right-hands, then Blackbeard shouldn't match with him. Blackbeard should match with Akainu while Kizaru vs. Shiryu (or Aokiji) happens.
However there is another possibility, in Jaya arc, Luffy took down Bellamy with one-shot after dodging Bellamy's attacks for sometime, while Teach took down Bellamy's right-hand Sarquiss with one-shot without even wasting any time unlike Luffy did with Bellamy.
If Luffy and Teach somehow fights the Marines simultaneously for some reason or luck, then if Luffy takes down Akainu, Blackbeard can take down Kizaru at the same time, but while Luffy struggles to beat Akainu, Blackbeard can defeat Kizaru easier in comparison with Luffy vs. Akainu.