In a baseball world that is clearly trending toward youth and positional versatility, it may seem that a 38-year-old designated hitter who can't really play the field anymore would struggle in free agency. After all, we saw a lot of that last offseason: Andre Ethier never found a job, Jayson Werth had to settle for a Minor League deal and Matthew Holliday sat out until July. 
Perhaps that's what's going to happen to Nelson Cruz this offseason, too. He turned 38 on July 1, and he's played just nine games in the field in the past two seasons. Cruz is not going to get a long-term deal, and since no National League team will seriously consider him, he might have a difficult time finding a spot at all. Yet unlike Ethier, Werth and others, Cruz has shown few signs of slowing down. He's been one of the foremost sluggers in the Majors for a full decade at this point. Sure, Father Time is undefeated. But what can we expect from Cruz going forward?
The first thing to remember is that we've all said that Cruz was overrated before, and we've all been wrong. After a successful run with Texas, Cruz managed to get just a one-year deal from Baltimore in 2014, and he was fantastic, hitting .271/.333/.525 with 40 home runs. He parlayed that into a four-year deal with Seattle, and the reaction was mostly negative, with the argument being that committing that much contract length to the age 34-through-37 seasons of a slugger who added no defensive value was overly risky.
Cruz, however, spent four seasons mashing, hitting 163 homers with Seattle, along with a .284/.362/.546 line. Despite Safeco Field's reputation as a hitters' park, no hitter has more home runs in the past four years. 

If you look at the underlying skills -- we like to use a metric called "Expected wOBA," which accounts for both quality of contact and amount of contact -- Cruz doesn't appear to be showing much decline. Keeping in mind that the Major League average Expected wOBA this year was .311, and that Mookie Betts led the Majors at .429, look at how consistently strong Cruz has been in the past four years.
2015: .377
2016: .397
2017: .408
2018: .395
But still, Cruz is 38. Can we really expect him to keep doing this for much longer? To figure that out, let's do what we did last winter for Lorenzo Cain and J.D. Martinez, which was to try to identify similar groups of players at the same ages throughout history to see how they'd aged. We expected both Cain and Martinez would have outstanding years in 2018, and each did exactly that. What about Cruz? 
We'll start by going back to 1945, the end of World War II, and finding hitters who took at least 1,000 plate appearances in their age 35, 36, and 37 seasons. There are 264 such hitters, and Cruz's three-season line ranks 21st. Of the 20 hitters ahead of him, a dozen are Hall of Famers. That's good!

But we can do better. There's a great deal of selection bias here (you're only getting 1,000 plate appearances at this age if you're a strong hitter to start with), and we need more similar players.
So let's limit it to the Wild Card era, since 1995, and just among hitters who were between 30 and 50 percent better than average in the three-year span between ages 35 and 37. (We're using Weighted Runs Created Plus for that last part, or wRC+. The Major League average is 100, and Cruz has a 142 wRC+ over the past three years, making him 42 percent better than average.) We'll also require a slugging percentage above .500, because we're looking for mashers, not Tony Gwynn.
That leaves us with 15 names aside from Cruz who we can reasonably say are rough comparables, and we're ignoring defense, because he's a DH and all that's going to matter is his bat. It's a fun list. 
Harold Baines
Ellis Burks
Andres Galarraga
Jason Giambi
Chipper Jones
Edgar Martinez
Mark McGwire
David Ortiz
Rafael Palmeiro
Jorge Posada 
Manny Ramirez
Gary Sheffield
Frank Thomas
Jim Thome
Larry Walker
Unlike when we looked at Cain or Martinez, we don't need to project far into the future. Cruz is strictly on a year-to-year basis at this point in his career. All teams need to worry about is whether Cruz is likely to keep slugging in 2019, and then '20 might be someone else's problem.
So how did this group of 15 end up doing? At age 37, this group, excluding Cruz, hit .282/.384/.533, a .917 OPS. From there ... 
At age 38
.269/.375/.482 (.857 OPS)
The injury-plagued McGwire retired, while Galarraga missed the year battling lymphoma, though he would later return to play five more seasons.
The remaining 13 were mostly very good, though not quite as good as at age 37. Twelve of them were above-average hitters, ranging from Burks' 110 wRC+ to Edgar Martinez's 157; Thomas hit 39 home runs for the 2006 Athletics. The only hitter who didn't play that well was Giambi, who hit a combined .201/.343/.382 (98 wRC+) for the A's and Rockies, though that didn't stop him from sticking around for five more years.
At age 39
.268/.361/.475 (.836 OPS)
A slight decline from the year before, but still a strong set of hitting seasons.
Galarraga returned, but Walker had retired, and Burks and Ramirez hardly played at all in their final years. Of the 11 who got at least 200 plate appearances, the results were mostly good. Martinez (.277/.403/.485, 141 wRC+) had another star-level year, as did Ortiz (.273/.360/.553, and 37 homers to go with a 139 wRC+). Posada, Giambi and Sheffield were the only ones who were below-average hitters, but none were disasters, all coming in only 5 to 10 percentage below league average.
At age 40
.282/.372/.495 (.867 OPS)
Obviously, no one's giving Cruz a three-year deal, but let's play this out. We're now down to 10 hitters, since Posada had called it a career, and the production remained outstanding, actually slightly better. Again, selection bias at work, but Cruz has earned his entry into this group.
Every single one of them had average-or-better hitting seasons. Every one. Ortiz (.315/.401/.620, 163 wRC+ with 38 homers) had one of his finest years in his final season, as did Baines (.312/.387/.533, 135 wRC+ with 25 homers) in his final year as a regular.

Beyond that, well, it doesn't matter. Cruz isn't getting a long-term deal, so we can worry about his 40s in 2020. But to this point, his peer group generally performed well. It's a great sign for him for the next few years, of course assuming health.
But none of that overcomes what will remain a big sticking point for Cruz, which is that there's relatively few landing spots for his services, assuming no National League teams will be interested. The Red Sox (Martinez), Yankees (Giancarlo Stanton), Indians (Edwin Encarnacion), A's (Khris Davis), Angels (Shohei Ohtani, Jose Pujols), Blue Jays (Kendrys Morales) and Rangers (Shin-Soo Choo) may not have a need. Rebuilding clubs like the Tigers, White Sox, Orioles and Royals may not see the point in adding a 38-year-old.
That leaves Cruz with four likely options.
Rays
The 90-win Rays were one of baseball's most stunning stories in 2018, and they really ought to be aggressive to build upon that in 2019. Tampa Bay's primary designated hitters in '18 were C.J. Cron and Ji-Man Choi, though it seems likely the arbitration-eligible Cron may be on the move and Choi has no track record to speak of before his nice run with the Rays. Neither is the hitter Cruz is. 
Since Cruz wouldn't require a long-term deal and the Yankees and Red Sox wouldn't likely be interested, it could be the perfect situation for Tampa Bay to add a big bat.
Astros
Evan Gattis is a free agent, and he hit only .226/.284/.452 in 2018, so there's an opening here. Now, the Astros may just prefer to give the job to Tyler White, who was outstanding (.276/.354/.533) in part-time play down the stretch, taking time from Gattis. Then again, Cruz taking aim at the short porch in Houston would be incredibly appealing, and White could end up taking time away at first base from soon-to-be 35-year-old Yuli Gurriel, anyway.
Twins
Minnesota designated hitters put up a line of only .239/.316/.373, the third worst in the American League. Two of the three players who shared time there are free agents (Joe Mauer, Logan Morrison) and the third, Robbie Grossman, is hardly a roadblock. This idea depends largely on whether Miguel Sano is ticketed for DH or if he can be healthy and productive at third base all year, but the Twins finished only 23rd in home runs in 2018. They could use the power.
Mariners
A return to Seattle might be the easiest answer, since Cruz has proven he can be productive there, but it might perhaps say something that no deal has yet been reached. The Mariners finished 21st in runs scored even with Cruz, and losing him would create a hole that Daniel Vogelbach or Ryon Healy would be unlikely to fill. Then again, Robinson Cano is 36 and might need some designated-hitter time himself, especially if the team views Dee Gordon as more of a second baseman than an outfielder going forward.