the mysterious connection between Saul Goodman and Lalo for years, thanks to a throwaway line of dialogue. The spinoff is now in the process of fleshing that bit out, having introduced Lalo at the end of season 4 and promoting him to series regular in season 5. He's taken a great interest in Gus Fring's cartel activities, doing whatever he can to undermine the Salamancas' nemesis within the cartel.
Of course, Gus is always one to match wits with an enemy and isn't easy to outsmart. He got ahead of Lalo by enlisting Mike's help, leading to Lalo being arrested at the end of "Wexler v. Goodman." This thread was left hanging to be resolved in a later episode, but it certainly looks like Lalo is going to be in need of legal representation. There's one obvious person he can turn to in this situation, though he may not for whatever Gus has planned next.
In all likelihood, Lalo will hire Jimmy to be his lawyer as he deals with the authorities. He knows Jimmy from the Krazy-8 case earlier this season, and Lalo did not intend for that to be a one-time partnership between the two. When Jimmy tried to talk his way out of future cartel endeavors due to his busy schedule, Lalo just said, "you'll make time" and drove off, so it's possible Jimmy will be Lalo's counsel against his will. That interaction felt like a seed being planted to develop further in the season and now there are only four episodes left (it could also be explored in the sixth and final season). But it goes without saying Jimmy representing Lalo isn't going to be a simple task.
Going back to that infamous bit of Breaking Bad dialogue, where Saul is absolutely petrified he's been captured by Lalo's associates, the big takeaway is things did not go particularly well there. Saul clearly believes Lalo holds some sort of grudge against him and has a score to settle, so one could theorize he lost the case and Lalo went away to prison. Saul's frantic plea in Breaking Bad, "It wasn't me, it was Ignacio! He's the one!" makes it sound like Nacho played a role in Lalo's verdict and Jimmy/Saul was aware of what was happening. , Nacho is in league with Gus, doing everything he can to protect his father from Fring's wrath. Gus could force Nacho to do something that proves Lalo's guilt; and since Nacho has his own familiarity with Jimmy, he could instruct Jimmy to handle things a specific way (similar to how Lalo wrote a script for Jimmy to give to Krazy-8). That would go a long way in explaining why Lalo puts the fear of God into Saul - he's been living scared that one day a (very) disgruntled former client is going to take frustrations out on him.
Getting dragged deeper into cartel politics is the last thing Jimmy needs right now, considering how things have reached a boiling point in his relationship with Kim. He wants to take care of his personal life first and foremost, but he may not have a choice. One of the best things about the Breaking Bad universe is how it doesn't shy away from exploring the consequences of the choices characters make. Jimmy decided to blaze a new path as Saul Goodman, seeking out the shadiest clients possible in Albuquerque's seedy underworld. There's no way Lalo would turn to Howard Hamlin, but Jimmy could be his guy.
Better Call Saul airs Mondays on AMC.