Major League Baseball is a young man's game these days. In 2015, players 30 and older combined for their least productive season since the 1994 strike, as FanGraphs' Dave Cameron recently showed.

Despite those shifting demographics, Adrian Beltre chugs along, an exception to the rule as he continues building on what already is a stellar Hall of Fame resume.

To put Beltre in context, consider that only seven of 29 position players (24 percent) who compiled at least five wins above replacement (WAR) last season, per Baseball-Reference.com, were in their age-30 season or older. Of 82 players with at least 3 WAR, 23 (or 28 percent) were in their 30s.

Beltre, however, posted 5.8 WAR at age 36, ranking behind only Joey Votto (31) and Ian Kinsler (33) among the 30-plus crowd. Not only did no player older than Beltre exceed 3.2 WAR, but only six others were worth even one win. No pitcher age 36-plus topped Beltre either, and only John Lackey (5.7) got anywhere close.

It's not as if 2015 was an outlier. Beltre was the first position player age 36 or older to accrue such a high WAR total since Chipper Jones and Manny Ramirez in '08, and aside from Barry Bonds, only one other player (Randy Velarde) has done so since 1988.

As Beltre prepares to report to Spring Training with the Rangers ahead of his 19th Major League season, here's a deeper look at what a long-underrated player has accomplished, and what still lies ahead.

• There has been some debate about the aging curve for hitters and exactly when the decline phase typically begins, but there is little doubt that most are better in their 20s than their 30s. And yet, Beltre now has 42.6 WAR in his 30s, compared with 41.2 before that.

Beltre wasn't exactly a late bloomer, though. He debuted in the Majors less than three months after his 19th birthday and stuck there, starting 152 games for the Dodgers and posting 3.9 WAR as a 20-year-old. So he put in more than 10 full seasons before turning 30 and only seven since. Compare that to Scott Rolen, a hot-corner contemporary who debuted in 1996 at age 21, posted 65 percent of his 70 career WAR before his age-30 season and played only 157 games after the age of 35.

• So just how unusual is it for a player to be as productive in his 30s as Beltre has been? In the integration era (since 1947), his 42.6 WAR from age 30-36 ranks ninth among position players, behind only Willie Mays, Bonds, Roberto Clemente, Hank Aaron, Stan Musial, Mike Schmidt, Jackie Robinson and Joe Morgan. Those are all Hall of Famers, with the exception of Bonds.

Since 1947, Beltre already sits 21st in WAR from age 30 forward and needs an additional 9.4 to climb into the top 10. He also is one of 11 players during that period to produce at least three seasons of 7-plus WAR in his 30s, having done so in 2010, '12 and '14.

• Beltre crossed the 400-homer plateau last season, joining Jones as the only third basemen to reach both 400 homers and 500 doubles. So what's next? With 560 doubles, Beltre is tied for 26th all-time and needs 19 more to pass Wade Boggs for second among third basemen, trailing only George Brett (665). Beltre, who has posted 32 or 33 two-baggers for five straight seasons, needs 40 more to join the exclusive 600 club. Currently, it has only 14 members, though David Ortiz (584) and Albert Pujols (583) could get there before Beltre.

• Speaking of milestones, Beltre is 233 hits away from 3,000. Not counting the 77 games he played at age 19, he has never collected fewer than 267 hits over back-to-back seasons. Of course, injuries are always a threat, and the cliff can arrive suddenly at Beltre's age. But despite playing through a torn thumb ligament over the final three months of 2015 -- following a stint on the disabled list -- Beltre raked after the All-Star break, batting .318/.376/.509.

After undergoing surgery on the thumb following the playoffs, Beltre recently described himself as healthy going into the spring. There also has been talk of a contract extension with the Rangers that would keep Beltre in Texas past 2016. In other words, Beltre seems to stand a strong chance of becoming the 30th player to get to 3,000 -- or 31st if Ichiro Suzuki (2,935) can arrive first. Among third basemen, Beltre already ranks fourth, needing 82 hits to pass Brooks Robinson. It's not out of the question he could wind up No. 1 at the hot corner, as he sits 387 hits behind Brett.

• If Beltre can manage 4.7 WAR in 2016 -- Steamer projects him for 3.9 -- he would pass both Jones and Brett, landing in fourth place all-time among third basemen behind only Schmidt, Eddie Mathews and Boggs. Of the top nine players on that list, only Jones (eligible 2018) and Beltre are not yet in Cooperstown, even at a position that doesn't always get the respect it deserves.

• Can Beltre keep his recent run going? Obviously, the odds are against him. Only 14 times since 1901 has a third baseman posted even three WAR in a season at age 37 or older, and the last to do so was Tony Fernandez back in 1999.

Regardless, based on what we have seen of late, counting out Beltre doesn't seem any wiser than trying to touch his head.

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Andrew Simon is a Sports on Earth contributor and a reporter for MLB.com. Follow him on Twitter @AndrewSimonMLB.

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