Even after the San Francisco Giants had first traded for Evan Longoria in December 2017, it was easy to wonder how long it would be before they had cause to regret it.

Just about six months, as it turns out.

Longoria hasn't been on the field for the Giants since June 14, when he broke his left hand on a hit-by-pitch. And up until then, the 32-year-old third baseman had just a .711 OPS, 10 home runs and, according to Baseball Reference, 0.3 wins above replacement.

The positive spin here is that there are bigger disasters than this elsewhere in Major League Baseball.

For example, Chris Davis (minus-2.1 WAR) is trending toward one of the worst seasons in history in just the third year of a seven-year, $161 million contract. Longoria's at least been better than that, and he had only $88 million remaining on his contract coming into 2018.

And to be fair to the Giants, Longoria won't actually be costing them $88 million. The Tampa Bay Rays kicked in $14.5 million as part of the deal and also took Denard Span and his $11 million salary off the Giants' hands. 

To be even fairer to the Giants, they couldn't have foreseen Longoria would be knocked out for a good portion of 2018 by a wayward Dan Straily fastball. They also get props for keeping Pablo Sandoval around. Him being a capable stand-in at third base is one of many storylines that explains how the Giants are hanging in the National League playoff race at 45-40.

At least where Longoria is concerned, however, that's about the extent of the "to be fairs." Trading for him was a gamble from the start, and it's already safe to disregard any notion of the deal ever paying off.

Consider this graph, which shows the progression of Longoria's WAR per 100 plate appearances throughout his career:

Between 2008 and 2011, he was an elite player who took home a Rookie of the Year award and three All-Star appearances. Then he became just a great player in 2012 and 2013, and then a merely good player between 2014 and 2017. In 2018, he's finally become a bad player.

Such is life when one starts out with a slick glove on defense and plenty of power and patience on offense, and then all three skills start to deteriorate.

Between 2008 and 2011, Longoria's 66 defensive runs saved were more than every defender except for Adrian Beltre and Brendan Ryan. But over the next six years, he managed a grand total of nine DRS.

Meanwhile, here's what happened with his patience (walk percentage) and power (isolated power):

• 2008-2011: 11.2 BB% and .240 ISO
• 2012-2017: 8.0 BB% and .195 ISO

The Giants surely weren't blind to any of this. What they must have figured was that Longoria could at least remain a good player for a couple more years. They may have even hoped he could become great again, perhaps by combining his 2016 power spike with his 2017 defensive renaissance.

Instead, Longoria has given them a ho-hum .188 ISO, gone back to regressing on defense with minus-three DRS and hit a nadir with his patience by way of a 3.7 BB%.

There's probably no saving Longoria's defense. He still has smooth actions and a good arm, but the difficulty he's had in converting difficult plays is indicative of a loss of range. And unlike the Rays could, the Giants can't give his legs occasional breaks with designated hitter duty.

His power is also likely beyond saving. The career-high 36 homers he launched in 2016 were the result of him joining the fly-ball revolution and cutting back on ground balls. It was a departure from the norm at the time, and he's been unable to sustain it in 2017 and 2018:

There's also the AT&T Park factor to consider. The often thick marine layer and the always deep dimensions that come with the territory have already proved to be quite capable of knocking down what fly balls and line drives Longoria can muster there:

The state of Longoria's power may also be having an effect on his ability to draw walks. For while the death of his walk rate has much to do with how he's become a more aggressive swinger, it also has to do with how pitchers have become more comfortable going right at him.

Before 2018, the difference between Longoria's strike zone rate and the average hitter's strike zone rate had never been higher than 1.3 percent. Now the difference is 1.8 percent, mainly courtesy of a huge uptick in four-seam fastballs.

These factors haven't just killed Longoria's walk rate. They've also led to more strikeouts, as he's gone from a 16.1 K% in 2017 to a 21.1 K% in 2018.

The ultimate reality is that Longoria was short on selling points even before he broke his hand. The Giants were coming face-to-face with a worst-case scenario in which their big offseason prize was following preexisting regressions right into his twilight years.

If that could happen to a healthy 32-year-old, then the prospects for a post-injury 32-year-old aren't so good. Likewise, it's hard to expect better things from his age-33 through age-36 seasons.

It's a tough break for the Giants. Although their decision to trade for Longoria didn't cost them too much, they're going to be paying for it for years to come.

Stats courtesy of Baseball Reference, FanGraphs and Baseball Savant.