In Season 4, episode 5, Mike and Jesse are out checking drop points. At one point in the episode Jesse mentions he could be "The guy", Mike then pulls over and rants to him about how this isn't in the cards: "You are not the guy, you're not capable of being the guy. I had a guy but now I don't. You are not the guy!"
In the bolded section, is it made clear who "The guy" is that he's referring to? I've thought it might have been Victor, he and Mike often worked together quite a bit.