The Astros have made it clear that they intend to upgrade their bullpen this winter, chasing Andrew Miller and David Robertson with significant four year offers before watching both sign with other teams. So this morning, they turned to Plan C, reportedly signing Luke Gregerson to a three year, $18.5 million contract, according to Bob Nightengale.

The big question hanging over this move, and the pursuits of Miller and Robertson, is why the Astros are spending money to sign free agent relievers. Expensive bullpen arms have historically proven to provide the lowest return on investment in baseball, and the Astros are not in a position to sacrifice significant future value for a modest short-term boost. Why would a team that has been so set on building for the future suddenly shift gears and sign an aging reliever who probably won’t still be an effective arm by the time the Astros are ready to contend?

Well, I’m just speculating here, but perhaps the Astros signed Gregerson with the clear intention of trading him this summer for something that could be a part of their future. As we see every July, the markup on useful bullpen arms is ridiculously high in-season, and with so many teams currently in go-for-it mode, the Astros are positioned to be one of the few teams able to take advantage of what should be a very strong seller’s market.

When everyone is buying, being the only team with stuff to sell is a great position to be in, but first, you have to have things that the buyers want. As long as he continues to pitch relatively well, contending teams will want Gregerson in July, especially if the Astros agree to pick up a bit of his future salary. And in effect, the Astros could essentially be buying themselves a pretty decent prospect.

Let’s say they hold him until mid-July, so they’d have paid him $3 million of his $6 million 2015 salary, then agreed to pick up $5 million of the remaining $15 million he was still owed. An acquiring team would only have to absorb $10 million in salaries for 2.5 years of relief work, which would look like a bargain at a time when there are going to be few other options to upgrade in-season. And so, the Astros could likely extract a solid young player in return, essentially buying that prospect for $8 million in salary.

The Astros have money, so they can afford to gamble the $18.5 million in guaranteed money that Gregerson can still be effective for a few months. If it doesn’t work out, well, they’re out $6 million per year in a few years where they probably weren’t going to win anyway, and premium free agents aren’t taking their money until they get a little more respectable anyway. Yeah, Gregerson could suck, and then they’d have “wasted” that money, but it’s only wasted cash if you could have spent it on something better. If no one wants to sign with the Astros, and the alternative was to not spend it, then it’s not a waste even if he’s lousy and nukes his own trade value.

If he’s not lousy, and his trade value is buoyed by the Astros willingness to pay down part of this contract in July, then the Astros might have just found a way to make themselves an even more attractive seller in a market where there is going to be very little competition.