The Giants signed Mike Kickham on Friday. This move will almost certainly have no impact on the Giants this year.
This isn't me snarking about Kickham, though his major league performance so far makes that pretty easy to do. This is me playing the odds on minor league free agents, who very, very rarely make it to the majors. It doesn't not happen, of course (proud of you, Vogey!), but on the whole, it's very rare and the mere fact that you recognize a name being stashed in AAA doesn't mean you'll see him in the majors
Let's look at the 2015 River Cats for an example. Of all the minor league free agent pitchers on the team, the only ones who made the Giants were Mike Broadway and Cory Gearrin (Broadway actually signed in 2014 and pitched a few games for Fresno that year, but he still counts). The others – including guys with significant major league experience like Kevin Correia, Clay Rapada, and Tommy Hanson – never got a real chance. There were different reasons for each of them: Correia opted out for a shot in the majors with the Phillies, Rapada's results were good but probably unsustainable, and Hanson was largely ineffective. That's not to mention the cup-of-coffee guys like Robert Coello and Curtis Partch, and the good-stuff-but-not-quite guys like Braulio Lara and Nik Turley. All of them theoretically could have made the majors. None of them did.
Due to injury and more injury and not-really-injury-but-we-gotta-get-this-veteran-off-the-roster-for-a-while, the 2015 Giants used four hundred starting pitchers and seven thousand relievers. Don't check those numbers. I'm sure they're right. But the team couldn't find a way to put Correia on the roster to maintain inventory, and they didn't look for a reason to call up Rapada, even with his shiny AAA ERA and all of their roster woes. Why? Because they didn't force the Giants to call them up.
The mission of a minor league free agent is simple: perform so well that the organization has no choice but to make him a big leaguer. That's what Broadway did last year in Sacramento: he was so absurdly dominant that when the Giants needed a reliever, it wasn't even a question who they'd bring from AAA. At that level, he was better than Hunter Strickland, and he was much, much better than the league. He was a human Thwomp. Mike Broadway forced the Giants to call him up in what, at the time, closely resembled a playoff race. No, Broadway didn't look great in the majors, but that's a pretty unlikely outcome for someone who both scouts and stats were drooling over.
Cory Gearrin also had a good year in Sacramento, and he got called up in September, in what kinda resembled a playoff race if you squinted, crossed your eyes, and tried to move the one pattern over the pattern right next to it so that you could see the 3D image. He didn't force the issue, and got a token "let's see what he's got" call-up after twelve new 40-man spots opened up in one day. He was interesting, and maybe he had potential, but there was a fair amount of luck involved in his being a major leaguer this year.
Mike Kickham is not back because the Giants were feeling nostalgic for a pitcher who couldn't get out of the second inning. Mike Kickham is back because the Giants like his stuff, and they're hoping that there's a way to harness it in AAA. Yes, it's entirely possible that he'll be very bad there, or he'll be okay, maybe he'll be pretty good, but none of that would be enough. If Kickham's not beating down the doors like Broadway was, then the absolute most he will get is the Hey Why Not Special that Cory Gearrin got this year. That's not bad! But it's not good either.
Minor league depth moves are nothing more than shoving a whole bunch of pocketknives behind the glass, hoping that if you need to break it one day in case of emergency, one of them will have an axe on it. Mike Kickham is one of those, and the glass will probably stay intact all year.