By Cliff Corcoran

As baseball's offseason continues to inch along at a seemingly glacial pace, there is a growing sense that this year's top free agents are competing not merely with one another, but with next fall's bumper crop of free-agent stars. That appears to be especially true near the top of this year's class. Just three of this offseason's top 20 free agents have come to terms on new contracts. That has prompted speculation that some teams may be loathe to make significant commitments this offseason when they could get more bang for their buck next year.

The 2018-19 free-agent class is notable for its headliners, a pair of young studs who won't be 26 until the 2019 season and could land the two largest contracts in Major League history. However, what makes it truly impressive is its depth, as evidenced by the list of the top 15 2018-19 free agents below. Not all of the players listed will make it to free agency next November. Some will sign extensions. Others might fall in the rankings due to injury, decline or a bad walk-year performance. However, not included on the list below are the players eligible to opt-out of their contracts after the 2018 season, a group that includes David Price, Mark Melancon, Jason Heyward, Elvis Andrus (who could take advantage of yet another thin group of shortstops) and Clayton Kershaw.

Here, then, is a preliminary ranking of next year's top 15 free agents, a list so deep that Andrew McCutchen and Adam Jones don't quite make the cut.

1. Manny Machado, 3B/SS

2019 Playing Age: 26

Machado is just three months older than Bryce Harper. He is more reliable in terms of health (Harper has played 150 or more games once in his career; Machado has done it in four of the past five seasons). He is more consistent in terms of performance (Harper has been worth less than 2.0 wins above replacement in two of the past four years; Machado has topped 2.4 bWAR every year since 2013). Machado also plays a position that is much more difficult to fill. True, both the 2017-18 and 2018-19 free-agent classes offer a strong group of third basemen, but Machado has expressed a desire to return to his natural position of shortstop, an extremely thin position in both free-agent classes. Machado started 43 games at short in 2016 in place of an injured J.J. Hardy and acquitted himself well, and his excellence at third base suggests the transition would be a smooth one. Meanwhile, over the past three years, Machado has hit .280/.338/.502 (123 OPS+) while averaging 35 home runs per season. Over that same span, no shortstop has hit 35 home runs in a season, while only Corey Seager (twice), Carlos Correa and Zack Cozart (in a likely career year) have surpassed a 123 OPS+ in a qualifying season.

2. Bryce Harper, RF

2019 Age: 26

Harper's ceiling is higher than Machado's, as evidenced by the 2015 season, when he became the youngest player ever to win his league's MVP Award, posting a 198 OPS+ and compiling 9.9 bWAR. Though his career has thus far been marked by injury and frustration, his 140 OPS+ ranks ninth among all active players with at least 1,000 plate appearances, and is tops among the 2018-19 free-agent class. With a strong, healthy walk-year, Harper will warrant a massive contract. That said, the Yankees trading for Giancarlo Stanton could have a negative impact on his market, no matter the strength of his 2018 campaign.

3. Josh Donaldson, 3B

2019 Age: 33

The 2015 American League MVP Award winner lost 38 games to a calf strain in early 2017, but he still managed to hit 33 home runs in 113 games. Over the past five seasons, he has hit .282/.377/.524 (144 OPS+), while averaging 33 home runs and 82 walks per year, and he is excellent in the field and on the bases, as well. From 2013-16, Donaldson averaged 7.8 bWAR per season. He needs a healthy, productive walk year to fight off concerns about his age, but there is no reason to think he won't deliver.

4. Charlie Blackmon, CF

2019 Age: 32

Blackmon finished fifth in a crowded National League MVP Award vote last month for a season in which he led the Majors in hits (213), runs (137), triples (14) and total bases (387), but that performance was no fluke. He was an All-Star in 2014 and hit .324/.381/.552 (130 OPS+) with 29 home runs in 2016, the latter a season in which he hit .313/.363/.563 with 17 of those home runs outside of Denver.

5. Brian Dozier, 2B

2019 Age: 32

Dozier hit 42 home runs in 2016, 40 of them while playing second base, one shy of the record at the position set by Atlanta's Davey Johnson in 1973. Over the past four years, Dozier has posted a 120 OPS+ while averaging 32 homers, 72 walks and 17 steals per season and playing an above-average second base.

6. Dallas Keuchel, LHP

2019 Age: 31

Keuchel struggled in the follow-up to his 2015 NL Cy Young Award campaign and lost time in 2017 to a pinched nerve in his neck, but he's still an elite ground-ball pitcher with the presence of an ace on the mound and ample postseason experience. He has posted an ERA+ above 130 in three of the last four years.

7. Nelson Cruz, DH

2019 Age: 38

Cruz is a bat-only player who will turn 39 on July 1, 2019, but what a bat! Over the past four years, Cruz has hit 13 more home runs than any other player in the Majors, batting .287/.359/.549 (147 OPS+), while averaging 42 home runs per season. Only six active players have a higher OPS+ than Cruz over that span (minimum 1,200 plate appearances). Harper, at 148, is one of them.

8. Adrian Beltre, 3B

2019 Age: 40

Beltre won't last forever, but after missing the first 51 games of the 2017 season with a calf strain, he was as good as ever for the remainder of the season, hitting .312/.383/.532 (135 OPS+) the rest of the way while playing a characteristically superb third base. The 2019 season will be Beltre's 22nd in the Majors, so he may be a one-year-at-a-time player from this point forward, but he has yet to indicate that he won't continue to be incredibly valuable. Bonus incentive: Beltre is on pace to hit his 500th career home run in 2019.

9. Ian Kinsler, 2B

2019 Age: 37

Kinsler could drop significantly in these rankings after the 2018 season. He had a career-worst season at the plate in 2017, and second basemen tend to hit a wall in their late 30s. Still, he was worth at least five wins above replacement every year from 2013-16, and his broad skill set (speed, defense, power) encourages optimism.

10. DJ LeMahieu, 2B

2019 Age: 30

LeMahieu is an elite defensive second baseman who has hit .319/.383/.430 over the past three seasons and will be among the younger players in this class (Harper and Machado excluded). Of course, after correcting for Coors Field, that batting line is only slightly above-average at a 104 OPS+, and even with the help of the thin air, there is almost no power there. Still, he can hit for average, will take his walks and hit .294/.352/.401 on the road in 2017, good for a 107 OPS+ relative to league-wide road splits. The 2018-19 class offers a deep group of second basemen, but LeMahieu is still near the top of that group.

11. A.J. Pollock, CF

2019 Age: 31

When healthy, Pollock is a five-tool centerfielder who can hit 20 homers, steal 30-plus bases, hit for average and play a Gold-Glove-worthy centerfield. Staying healthy has been a problem, however. He has played just 124 games over the last two years due to elbow and groin injuries and desperately needs a strong, healthy walk year to maximize his free-agent value.

12. Drew Pomeranz, LHP

2019 Age: 30

Pomeranz quieted concerns about his health in 2017 by making 32 starts and largely replicating his breakout 2016 season. He now has a 132 ERA+ over the last two seasons with 360 strikeouts in 344 1/3 innings, surviving the move to the designated-hitter league and a less pitcher-friendly ballpark in the process.

13. Daniel Murphy, 2B

2019 Age: 34

Murphy has hit .334/.387/.569 (145 OPS+) in his two seasons with the Nationals, leading the league in doubles both years and finishing second in the 2016 NL MVP Award voting. However, his play in the field has undermined his production at the plate. Come 2019, he may need to move off the position. Fortunately, if he can keep up that pace at the plate, he'll be perfectly viable at first base or designated hitter, albeit on a shorter contract.

14. Craig Kimbrel, RHP

2019 Age: 31

Kimbrel rediscovered his most dominant form in 2017. That's saying something, as he has authored three of the five highest single-season strikeout percentages in Major League history. Included among those is his 49.6 percent this past year, which ranks third all time, but only second in his own career. He is back in the conversation about the best relief pitcher in baseball, but one of his rivals for that title is also in this free-agent class.

15. Andrew Miller, LHP

2019 Age: 34

Over the past four years, Miller has posted 1.72 ERA (248 ERA+) and 0.79 WHIP while striking out 14.5 men per nine innings with 6.28 strikeouts per walk. In the postseason, over the same span, he has posted a 1.10 ERA and 0.77 WHIP with similar peripherals while averaging nearly five outs per appearance over 20 games. Untethered from the closer role, he might be the most valuable reliever in the game.

Honorable mention: center fielders Adam Jones and Andrew McCutchen; relievers Zach Britton, Cody Allen, Brad Brach, David Robertson, Ryan Madson, Kelvin Herrera and AJ Ramos; lefties Gio Gonzalez, J.A. Happ and CC Sabathia; first baseman Joe Mauer; second baseman Logan Forsythe; catcher Yasmani Grandal; utility man Marwin Gonzalez; outfielder Michael Brantley

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Cliff Corcoran is a Sports on Earth contributor and a regular guest analyst on MLB Network. An editor or contributor to 13 books about baseball, including seven Baseball Prospectus annuals, he spent the last 10 seasons covering baseball for and has also written for USA Today and SB Nation, among others.