How many future HOFers will play in 2018?

For any given game in the upcoming 2018 season, no matter which two teams are playing, there's a possibility you'll be watching a future Hall of Famer. Often, it will be easy to identify who that player will be, as there are plenty of stars with tons of awards on their shelves already.
But sometimes, it won't be so obvious, because you might be seeing a struggling rookie at the start of their career who, after a period of time, eventually turns into the next Randy Johnson or Rickey Henderson.
We can't sit here today and predict for you who will be enshrined in the Hall of Fame class of, say, 2041. Instead, what we can do is take a look at today's current players and give you a good idea of who might be in that conversation some day.
First, we have to estimate how many Hall of Famers we should be expecting. When we did this in 2017 and '16, the numbers indicated that there were an average of 31 future Hall of Famers playing in each season. Between 1946-86, for example, it was between 27 and 36 future legends playing literally every single year. While it's fallen since, that's in part because some of the stars of the following era are the players being considered for induction right now, like Edgar Martinez (debuted in 1987) and Larry Walker ('89).
So, who in 2018 may potentially land in Cooperstown some day? We can break it down into tiers, and for ease of reference, we'll show each player's current Wins Above Replacement, per FanGraphs. It's not the end-all be-all of a player's value, but it's the best we've got, and it does a strong job in estimating how productive they were. For reference, the average Hall of Famer put up between 50-70 WAR in their career. The best of the best, like Babe Ruth, topped 160 WAR.
Before we get to the 2018 list, let's note that you won't see Chase Utley (65 WAR) and Ichiro Suzuki (58 WAR) here. Ichiro seems like a slam dunk, and Utley has a strong case, but they're each currently without a team, so we don't know if they'll end up playing again in '18.
The absolute locks

1. Albert Pujols (89 WAR)
   
2. Adrián Beltré (84 WAR)
   
3. Miguel Cabrera (67 WAR)
   
4. Clayton Kershaw (58 WAR)
   Pujols and Cabrera are two of the top 10 right-handed hitters ever. The fact neither had a strong 2017 doesn't matter much, because they are obvious first-ballot locks, and you'll see them play in '18. Beltre reached 3,000 hits in 2017, still has a shot at 500 homers and when he retires, WAR will consider him one of the five best third basemen of all-time. He'll get in easily.
   Kershaw is a new entry to the list of slam dunks, because 2017 represented his 10th year in the Major Leagues, making him eligible for induction if he were to retire today. He won't be 30 until March, but with three Cy Young Awards, as well as seven straight top-five finishes, and an MVP Award under his belt, the question is less, "Will he make Cooperstown?" and more, "Will he be the greatest pitcher ever?" Needless to say, his induction seems assured.
   Mike Trout's personal tier

5. Mike Trout (54 WAR)
   Only entering his age-26 season, we can't really say he's "in" in the same way we can about Pujols, but let's be honest: At this rate, he's going to be considered the best player of his generation. Remember, he entered 2017 with five straight top-two finishes in the MVP balloting, and he then proceeded to have his best season yet on a rate basis. Despite his youth, he's already out-produced Hall of Famers like Jim Rice (50 WAR), Orlando Cepeda (50 WAR) and Ralph Kiner (48 WAR). He remains, somehow, underrated.
   Over-30 stars working on strong cases

6. CC Sabathia (65 WAR)
   
7. Justin Verlander (57 WAR)
   
8. Zack Greinke (54 WAR)
   
9. Joey Votto (53 WAR)
   
10. Robinson Canó (53 WAR)
    
11. Evan Longoria (50 WAR)
    
12. Dustin Pedroia (49 WAR)
    
13. Max Scherzer (44 WAR)
    
14. Andrew McCutchen (44 WAR)
    
15. Buster Posey (37 WAR)
    
16. Yadier Molina (35 WAR)
    
17. Paul Goldschmidt (32 WAR)
    Some of these guys are going to make it in. A few will, actually. But don't forget how quickly this can change, also. A few years ago, you'd have expected David Wright, Ryan Braun and Troy Tulowitzki in this group, and now it's difficult to see any having a shot.
    Cole Hamels, Félix Hernández and Jon Lester might belong on this list, but it's more complicated than ever to know how future voters will evaluate starting pitchers, as they pitch fewer and fewer innings. Are these three all-time greats, or just very good? Does Hernandez have a rebound in him, or will he be the Andruw Jones of the mound, because his last really great season came at age 29, back in 2015? Does David Price have a second act in him, or was '17's arm trouble the beginning of the end?
    That's not even to mention the over-30 stars who are among the game's truly elite right now, but probably got too late of a start to compile the counting stats that are usually required. We're talking about Josh Donaldson, who didn't have his first great year until he was 27, Daniel Murphy, who broke out as he turned 30, Corey Kluber, who had his breakthrough at 28, or Justin Turner, who was a non-roster invite heading into his age-29 season. The talent is undeniable, but is there time left?
    None of the players here are locks, and some have more work to do. Pedroia, McCutchen and Longoria, in particular, probably need another great season or two. Verlander enhanced his case with his performance helping Houston to a title, but he's not quite over the line yet. Molina won't have the stats, but his case will be improved by his reputation as a leader. Meanwhile, we want so badly to say that Votto is a lock, and it works in his favor that the evolving electorate seems more likely to value the skills he excels at. In another year, he very well may be.
    30-and-under players on the right path

18. Chris Sale (35 WAR)
    
19. Giancarlo Stanton (34 WAR)
    
20. Madison Bumgarner (30 WAR)
    
21. Bryce Harper (27 WAR)
    
22. Manny Machado (26 WAR)
    
23. Jose Altuve (26 WAR)
    
24. Freddie Freeman (25 WAR)
    
25. Anthony Rizzo (24 WAR)
    
26. Kris Bryant (22 WAR)
    
27. Nolan Arenado (21 WAR)
    
28. Mookie Betts (20 WAR)
    
29. Craig Kimbrel (18 WAR)
    
30. Kenley Jansen (17 WAR)
    
31. Aroldis Chapman (16 WAR)
    The younger the group gets, the more difficult this exercise becomes. Not only are there more outcomes for career paths, but it's harder to know how voters may look at different kinds of contributions -- don't forget, many of these players won't be eligible for another 15 or 20 years.
    It's a fun group, though. Harper and Machado have accomplished so much so young that they almost stand apart, while Betts, Bryant, Rizzo, Altuve and Freeman are among the brightest under-30 stars in baseball. They just need to keep that up for another decade, or more. It's not easy.
    The bottom trio is an interesting subsection, because WAR isn't an ideal metric for relievers, and the simple definition of what a reliever even is seems to change regularly. That Kimbrel, Jansen and Chapman compile saves doesn't really matter much. That they are each making a case to be considered among the most dominant relievers who ever lived, even up there with the great Mariano Rivera, does. At least one, and maybe more, will get to Cooperstown.
    The "two great years or fewer" young field

32. Aaron Judge
33. Corey Seager
34. José Ramírez
35. Carlos Correa
36. Francisco Lindor
37. Cody Bellinger
38. Alex Bregman
39. Byron Buxton

40. Ronald Acuna
    
41. Shohei Ohtani
    42. Michael Conforto
    43. Xander Bogaerts
    44. Noah Syndergaard
    45. Gary Sánchez
    Look at these names. We're looking at four Rookie of the Year Award winners here, some of the most highly anticipated prospects in baseball and multiple first-round Draft picks who have already made an impression on the Major Leagues. You can almost guarantee that someone from this list -- or not on this list, but who will play in 2018, like Walker Buehler, Luis Severino, Andrew Benintendi or Rhys Hoskins -- will make the Hall of Fame someday.
    But who? Or how many? It's impossible and unfair to know for players this young. Judge could repeat his magical 2017 endlessly, or he could be one of history's all-time great one-hit wonders. The young shortstop trio of Correa, Seager and Lindor all look like they have what it takes to be the next Mickey, Willie and the Duke, yet the oldest is just 24. So much can go wrong. You can't possibly know.
    Obviously, we've named more than 31 players. Even more obviously, not everyone here is getting in, and someone who will appear in 2018 who we haven't even brought up will eventually get in. That's the point, though. You can't possibly know how all these careers will turn out. All you can say for sure is that you could throw a dart at literally any game on the schedule and potentially see greatness.