Danny Darwin was a fifth starter in 1998, and he was bad. Lo, how he was bad. If he were replaced with Kirk Rueter's worst year as a Giant, there wouldn't have been a need for the one-game playoff against the Cubs. Also, if Neifi Perez didn't hit a ninth-inning homer off Robb Nen at Coors Field, there wouldn't have been a need for the one-game playoff. If the robot I sent back in time to sterilize Neifi Perez's dad hadn't developed consciousness, and learned of the Four Noble Truths through intense study with Shunryu Suzuki....but that has nothing to do with fifth starters. Let's start over.
There aren't good comparisons for Brad Hennessey to be found in the past decade of Giants fifth starterdom. Darwin was old, and never really had his moments when he was young. Ryan Jensen almost seems to be a good comp, but it was always obvious that Jensen's ceiling offered nothing but a second-story view. The draft pedigree of Hennessey creates a superficial separation, and the sinker/slider combo definitely holds more promise than anything Jensen featured. Joe Nathan's arm was better than Hennessey's, but he didn't really know the first thing about pitching when he was a fifth starter.
Hopefully, Hennessey won't disappear into the Where Are They Now? file like Nathan did. The Giants aren't expecting Hennessey to set the National League ablaze, but can realistically hope for something like an average pitcher. Hoping is one thing, but it's debatable what they should expect. Most, if not all, of the community projections here will fall into the Mark Gardner spectrum, which is:
There is a downside to Brad Hennessey, and it's the reason I mostly ignored him as a prospect coming through the system. It's hard to be even an average pitcher with a strikeout rate as low as Hennessey's. I do buy into the conventional wisdom about sinkerballers, to a point. I can believe pitchers like Julian Tavarez and Derek Lowe induce enough groundballs to make up for a lack of strikeouts. It's just silly to apply that hope to every pitcher with a two-seamer. Hennessey does have a good sinker, and it's entirely possible he can succeed by allowing the ball to be put in play. But the margin for error is slim. I'll continue to underrate him until he proves me to be an idiot: