Why Are Projection Systems So High on Jhoan Durán and Griffin Jax?

You might have heard that the Twins are projected by FanGraphs to have the No. 1 bullpen in baseball this season. It's been a frequent talking point, both because fans have little else to discuss and because there seems to be a broad disconnect regarding the caliber of this unit. Today I wanted to dig a little bit into WHY projection systems view the Minnesota relief corps so favorably, even after they finished 19th in the majors last year with a 4.12 ERA and have made zero additions this offseason.

When you start parsing out the individual projections, what it comes down to is that systems like these are extremely high on the top two arms in the Twins bullpen: Jhoan Durán and Griffin Jax. For example, FanGraphs projects Durán to be worth 1.7 fWAR this season and Jax to be at 1.3 fWAR. That combined total, 3.0 fWAR, is higher than the projections for the entire bullpens of 17 different teams.

Here is the total pool of relief pitchers who are projected by FanGraphs to produce 1.3 fWAR or more in 2025:

• Mason Miller (2.1)
• Jhoan Durán (1.7)
• Félix Bautista (1.7)
• Edwin Díaz (1.6)
• Ryan Helsley (1.5)
• Josh Hader (1.4)
• Griffin Jax (1.3)
• Emmanuel Clase (1.3)
• Matt Strahm (1.3)
• Jeff Hoffman (1.3)

This really puts into context how high-powered the back end of Minnesota's bullpen can be: the Twins boast two of the top 10 projected relievers according to FanGraphs. So, what is it about Durán and Jax that make them such darlings in the eyes of these models, which evaluate based on historical performance, age curves, peripheral stats and predictive analytics? Here's a quick breakdown of the factors influencing each:

Jhoan Durán

Durán is among the most dominant relievers in baseball, and projection systems recognize that by weighing multiple key indicators:

• Elite stuff: Durán's fastball velocity (100+ mph) and splinker movement create extreme strikeout and weak contact tendencies. Stuff+ models (like those from Eno Sarris at The Athletic) grade his arsenal as among the best in MLB.
• Underlying metrics: Yes, Durán posted an underwhelming 3.64 ERA last year. But he does the things these models want to see. His xERA, xFIP, and SIERA have consistently shown that premier performance is sustainable. His ability to miss bats (30%+ K rate) while limiting walks and home runs keeps his projections strong.
• Durability and usage: Once plagued by injuries, he has made 58+ appearances in three straight seasons, and has held up well despite a minor dip in velocity.
• Expected regression to the mean: While relievers often show variance year to year, projection models hedge against outlier seasons. If Durán had a slightly "off" year in 2024 (even by his standards), models would likely expect a rebound.

Griffin Jax

Jax has transformed into a high-leverage weapon, and projections recognize him as a valuable setup man:

• Swing-and-miss arsenal: His overpowering sweeper ranks among the best in baseball in Whiff%, and he tunnels it effectively with his fastball. Projection models reward this ability because it sustains strikeout rates.
• Improved walk rate: Jax has cut his BB% each year, a trend models favor since control metrics are more stable than pure ERA.
• FIP and xFIP stability: Even when his ERA has fluctuated, his peripheral stats (FIP, xFIP, SIERA) remain strong, indicating he’s not overperforming by luck. 
• Leverage role: The Twins trust him in high-leverage situations, meaning he’ll consistently get innings in the 7th and 8th with high strikeout potential. And he's consistently shown he can deliver in those spots.

The relief pitcher position is highly volatile, with a great deal of year-to-year variance. Naturally, this makes performance difficult to confidently predict. But the bottom line is that Durán and Jax both excel in the areas that drive positive outcomes, and are in their physical primes with strong bills of health. There just aren't many relief pitchers around the league for whom that is true, as the list above indicates. 

None of this really matters much when the rubber hits the road, of course, but as we look ahead to the 2025 season it's a nice jolt of encouragement. Also, I would note that front offices around the league are using similar metrics and projection systems as FanGraphs, so the fact that both relievers grade out so favorably would seemingly only raise their appeal as trade targets, if in fact that's on the menu. 

Where do you stand on the top two Twins relievers heading into this season? Do you agree with the models or do you think they're exaggerating the team's strength at the back end. Would the Twins be wise to sell high on either? Let's hear from you in the comments.