HOFer?
Chapman and Jansen rate 6th and 7th in fWAR among relievers all time, just ahead of Billy Wagner. Top 5 are all in (Rivera, Gossage, Hofffman, Fingers, and Smith). It's a little more coin-flippy after Wagner among #9-#18: Doug Jones, Craig Kimbrel, Tom Henke, Eck, Joe Nathan, Hoyt Wilhelm, Lindy McDaniel, Papelbon, Bruce Sutter, and David Robertson.
Jay Jaffe ranks Jansen as a better candidate than Chapman by his R-JAWS, which uses bWAR, WPA, and "situational wins" (WPA/LI). He calls Jansen the best reliever currently outside the HoF on that basis. He'd be 4th on WPA among HoF relievers. He lumps Chapman, Kimbrel, and David Robertson close together on R-JAWS but says Chapman is substantially strengthening his case currently. Robertson's lack of saves will hurt him.
https://blogs.fangraphs.com/cooperstown-notebook-the-2025-progress-report-part-i/I think he's got a better shot than Jansen and Kimbrel. I just think the overwhelming fastball velocity gives him more glamour than the others. Add in the NYY time, too, as a plus. Jaffe notes may get punished by some voters for the domestic violence accusation in 2016. Oddly, all 3 of Kimbrel, Jansen, and Chapman pitched in Boston.
