Saul connected Walt and Gus, yes, but I assumed that Mike was the conduit for that. I just assumed Gus would want to avoid at all costs being seen around someone like Saul, who exists to serve the exact type of person Gus wanted to avoid being seen as at all costs. Like, Mike was how Gus navigated those waters without getting wet.
Again grain of salt that because maybe I forgot some scene with them together...