In typical MLS fashion, the trade was facilitated by bizarre, arcane rules and the specific dollar amounts involved were not reported. So, with a major asterisk placed on my evaluation by virtue of that uncertainty and an anticipated transaction that hasn't been completed yet, I think we may well look back on this trade as a proper fleecing of the Lions by the Quakes.
The terms are complicated, and there are many different levels of analysis, so I'll break it down into the categories that I use to evaluate:
The players themselves
Pérez-García, for all his creative spark, was inconsistent, not always efficient, a defensive liability, and not fit enough to contribute more than 60 minutes. Statsheads (like American Soccer Analysis) loved him, often citing his large "key passes" numbers, but the truth is he was never on the same level as fellow creative Argentine MLSers Mauro Diaz, Diego Valeri, or Javier Morales. He had already fallen down to third on the pecking order of wide players, and it's hard to argue that he's better than either Simon Dawkins or Alberto Quintero. Designated Player or not, the Quakes were trading away a backup.
Cerén put together a remarkable 2015 season that shows what he looks like at his best: a stout, reliable defender who has an eye for the pass from deep and on-the-ball skills that actually closely resemble a right-footed version of Aníbal Godoy. He was named MLS's "Latino del Año" in 2015 ahead of all sorts of much higher-profile names, and close observers of MLS echoed those sorts of plaudits. On the other hand, 2016 has been a big step backwards for the him, as his numbers have gone down across the board. Two mitigating factors to the decline include the fact he's been asked to play out of position more frequently this year (he's performed just fine when allowed to play DM), and he's been tasked with protecting Orlando's simply dreadful back line, which would be a tall order for anyone. On the whole, he's definitely MLS-starting-caliber, and I suspect he might look better in Dominic Kinnear's system than Adrian Heath's.
The other factor here is personality. Cerén has a scrappy life story and a reputation for intense application and a hard-working approach. He joined OCSC when they were still in USL, and from brief conversation with him when he arrived in San Jose on Thursday, he appeared to have the kind of attitude that Kinnear likes in his players. The El Salvador national team must feel similarly, since they named him Captain.
Pérez-García, on the other hand, was consistently chafing against the club's all-action, defense-first, low-individuality persona, and on more than one occasion appeared petulant about not playing the role he wanted. Put simply, it seemed to me that Pérez-García wasn't an ideal fit and wanted out, so the chemistry and attitude of the team stand to benefit. Just to be clear, I'm not insinuating that Pérez-García wasn't well-liked on a personal level (and in fact I've gotten the exact opposite impression); it's a purely on-pitch issue.
Impact on the roster and playing system
The positional exchange (giving up a creative attacker for a defensive midfielder) feels a bit bewildering for a team whose primary struggle has been putting the ball in the back of the net. Then again, precisely this criticism was leveled against the signing of Aníbal Godoy almost exactly one year ago and proved misplaced.
As far as I can gather from Kinnear, the motivation here is that he wants to play a system with two deeper central midfielders, and he only has two that he likes for the position (Godoy and Fatai Alashe). Since both players are facing card accumulation suspensions, and minor injuries or fitness issues are inevitable, he wanted a third option he could trust. He even specifically referenced wanting to avoid continuing to shoehorn Dawkins or Tommy Thompson into deeper central roles which, I agree, are neither ideal for those players personally nor the team as a whole. In this way, Cerén's arrival may well give those two attacking players the freedom to stay farther forward much like Godoy's acquisition allowed Chris Wondolowski to push up into a true striker position down the stretch in 2015.
Beyond the names I've already mentioned, while there are technically others who could play defensive midfield such as Marc Pelosi (long-term injury) or Matheus Silva (19 years old, on loan), no one is currently a realistic option to play at an MLS-starting-caliber level at this moment. Theoretical depth isn't depth. Depth you can write in the team sheet is.
Moreover, people who complain about the overabundance of defensive midfielders seem to have forgotten the huge glut of attacking midfielders/wide players that Pérez-García was in the midst of: Dawkins, Quintero, Cato, Thompson, and Salinas. If anything, that was the most bloated part of the squad, even if it wasn't as productive as fans would like. To get more out of it, you either have to improve top-end quality, or improve the players at other positions on the pitch, not hang on to your third-best option.
One player on whom the impact is unclear, but potentially very favorable, is Tommy Thompson. Tommy just got a major competitor for minutes out of the way, and will no longer be asked to play out of position. He seems to have fallen out of favor since the beginning of June, but I could see this move actually making it better for him on the field.
Accounting Instruments/Facilitating Future Transactions
Pérez-García's Designated Player tag will remain with San Jose (it's unclear whether this is due to MLS rules about amortizing transfer fees or simply what it took to get Orlando to do this deal), but due to an obscure MLS rule about season-ending injuries and Clarence Goodson's season-ending surgery, Orlando was allowed to trade cap space to San Jose in exchange. An international slot went the other direction for the end of the year, leaving the Quakes with one to play with, as before. That cap space partially helps cover the cost of Cerén himself, but Kinnear confirmed that it went beyond that such that the team could go on and acquire another player. As such, in the final evaluation of this trade, one must include any subsequent free agent signings that it facilitated as one of the "assets" the Quakes got in return.
Kinnear made it fairly clear in his press conference, and at training the next day, that a forward has been the long-time target of such an acquisition, rather than a midfielder like Jamie O'Hara, who is currently on trial with the club. Using a combination of the newly-acquired cap-space, the discounted cap-hit of a mid-season acquisition, and Targeted Allocation Money, the club could bring in a player that would in normal circumstances be making something in the lower range of the Designated Player bracket. If talented striker could be found for such a price, that would be transformative for this team's playoff chances.
Of course, this is where the asterisk comes from: if it's a player-for-player swap, I like this transaction a bit, and would give it something like a 6/10. But if the Quakes can add Cerén plus an impact #9 because of this move? It's a home run.
Pérez-García, at 31 years old, was entering the last few months of his deal. Cerén, on the other hand, is in the first year of a deal that offers Quakes control for up to 4 years, and is just 26 years old. He also has a salary about $100,000 less per year than the Argentine, freeing up more space on the cap. From a long-term roster planing perspective, he's a much better asset.
Kinnear denied that this sort of thinking played a primary role in the transaction, although the responsibility for these considerations is admittedly more the purview of the GM and Technical Director than the coach. However, for roster nerds like me, it seems like a clear victory to get a young player for years in exchange for an older rental.
Eventually, the Quakes may experience a bit of a glut in central midfield entering the 2017 season, assuming that Pelosi comes back healthy. Kinnear said he wasn't worried about that sort of glut forming in the future, that he'd deal with it when it arose, and specifically referenced Marc Pelosi as a guy who can play other positions. The potential situation does concern me, but I won't hold it against this transaction unless the Quakes manage it poorly once it arises.
The Bottom Line
This transaction swapped a want-away backup at an overstocked position who had just a few months left on his deal for a starting-caliber player at a position of need locked into a cheap price for the long run. Oh yeah, and it came with enough cap space to make a move for a badly-needed striker.
There are still things that have to fall into place, hence the asterisk, but that's a home run, for me.