WAR for relievers isn't the best, but bear with me for a second. Here's the top 10 relievers by fWAR just two seasons ago, and their current status:
1. Kenley Jansen Dodgers
2018: 0.3 WAR
2019: 0.9 WAR
Once one of the premier relievers in the game, now seen as a liability on the best team in baseball
2. Craig Kimbrel Red Sox
2018: massive drop off to 1.3 WAR, awful in the playoffs
2019: unsigned for the entire offseason and midway through the year, -0.6 WAR
3. Roberto Osuna Blue Jays
2018: DV scandal, 1.1 WAR
2019: 1.0 WAR, has gotten worse across the board
4. Corey Knebel Brewers
2018: ERA ballooned but still good otherwise, stupidly demoted, 1.0 WAR
2019: TJS
5. Pat Neshek Phillies/Rockies
2018/2019: has pitched a combined 42 innings, 0 WAR
6. Chad Green Yankees
2018: 1.7 WAR, slightly less effective but still excellent
2019: 0.9 WAR, demoted once, turned into opener, HRs skyrocketed
7. Andrew Miller Indians
2018: injured, 0.4 WAR
2019: -0.6 WAR, his constant usage in the regular season + postseason caught up to him
8. Felipe Vazquez Pirates
2018: 2.1 WAR
2019: 1.8 WAR (still a month left to go remember), is still one of the top relievers in the game
9. Mike Minor Royals
2018: 2.5 WAR as a solid starter
2019: 4.3 WAR (!!!) in a career rejuvenation breakout
10. Anthony Swarzak White Sox/Brewers
2018/2019: -1.1 WAR
You can go and take a look at this year's top 10 for comparison. Moral of the story: relievers are extremely volatile so don't invest heavily on them.