I don’t know why, but I’ve spent more time thinking about the Miami Marlins than any other team this winter. It started when the Marlins came to the end of the season with a not-terrible record of 79-83 – three games better than the Braves! – with some interesting pieces looking forward.
Then two Marlins showed up during my search for the next one Geraldo Perdomo. Then I kind of talked myself into thinking that Miami would be a lucky free agent who signed out of competitiveness – just like in 2002. But it turns out they’re not even making a token effort to spend money. They then traded their surplus pitchers to shore up their anemic lineup, which seemed like a fine compromise at the time, even if it weakened their biggest strength.
But then the Marlins thinned out that rotation even further, shipping Ryan Weers to the Yankees for four prospects. So now the Marlins are in a position where Janson Junk is back in their presumptive Opening Day rotation. How coincidental, because I’ve been wanting to write about Junk for a while.
Like I said, it’s been a weird year.
Junk himself is a bit of an oddity; players like him spark an irresistible curiosity in the kinds of people who sign up to write for FanGraphs. Specifically, Junk didn’t run with anyone this year; he finished the season with only 13 walks in 110 innings. His 2.9% walk rate was the lowest among pitchers who threw 100 or more innings in 2025, and the third-lowest in any 100-inning season in the 2020s, trailing only George Kirby in 2023 and Bryan Woo in 2024.
There must be something in the water in Seattle; Junk played his college ball at Seattle University, where he was a 22nd round pick in 2017. That’s the kind of small school where Junk would normally go down as a legend for merely making the majors; in fact, he is one of only five Redhawks to ever make it to the Show.
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Unfortunately, one of Junk’s teammates in college was Pull Skubalwhich has overshadowed him a bit.
The guy who never walks anyone out is a great hook, so David Laurila spoke to the right-handed Marlins in August. He talked about the new handles he used on his switch and sweeper, and how he refined his control by training at Driveline (shout out Seattle again) over the winter.
At the end of the season, Michael Rosen delved into the discrepancy between Junk’s position at the top of the walkrate leaderboard and his appearance at the bottom of the chart in Michael’s custom-built command metric, the Kirby Index. He found that Junk’s arm angle was all over the place, but bizarrely it had no detectable effect on the vertical movement of Junk’s fastball. I’m not going to go into that much detail because the main number that interests me about Junk is his FIP.
In 2025, Junk posted an FIP of 3.14, which was 30th among 199 pitchers with 70 or more innings. That’s good for everyone; the man who was one spot ahead of Junk on the FIP rankings was Hunter Brownwho finished third in the AL Cy Young voting. That is exceptional for the Marlins’ fifth starter.
As you know, FIP has three inputs: home runs, strikeouts and walks plus batters hit. Junk had the lowest walk rate of any regular starter and he faced only four batters all season. But his strikeout rate, 17.2%, was 170th out of 199 among pitchers with 70 or more innings. Those are quite a few extremes. What about the third input, home runs?
Junk did well here too. He allowed just eight dingers in 2025, for a HR/9 ratio of 0.65. That’s good for 27th in the league, with a minimum of 70 innings. But that actually underestimates how good Junk was at keeping the ball in the yard. Many of the guys before him on that list were relievers or groundball gluttons, whose fastballs came off the hitters’ bats and immediately dug into the earth in search of oil.
Junk is not that guy. In his review of Junk’s arm angle, Michael mentioned the name of Trey Yesavagewhose combination of a high release point and a nuclear splitter made him an overnight celebrity last October.
A guy with a great splitter should get a lot of groundballs, right? Yesavage did that during his brief stint in the Majors, but in 25 minor league appearances he actually had a slight fly ball bias: 0.87 grounders for every fly ball. It’s not just the splitter, it’s the four-seam with rise and cut that hitters can get under.
Junk doesn’t throw as hard, throwing three breaking balls to Yesavage’s, but he has many of the same characteristics: more rise and cut than average on the four-sieve, and a GB/FB ratio that’s in the range of even.
If you look at HR/FB%, Junk was 11th in the league with a minimum of 70 innings and third out of 127 with a minimum of 100 innings. Only 6.0% of his fly balls left the park.
HR/FB% is a bit like BABIP, in that about 15 years ago the conventional wisdom was that it was random. As our understanding of pitching has improved – especially our ability to gauge the quality of contact – that’s not entirely the case anymore. Still, the null hypothesis is that a huge deviation from the norm in HR/FB% (league average last year was 11.9%) is likely a fluke and ripe for regression.
Is there anything Junk is good at when it comes to reducing the quality of contact on fly balls?
Junk provides a lot of contact, and especially a lot of hard contact:
The quality of contact from Janson Junk
| Stands | Contact% | Severely affected% | EV90 | Walk% |
|---|---|---|---|---|
| Value | 83.4% | 47.3% | 106.3 | 8.5% |
| Rank | 119th | 118th | 119th | 56th |
Minimum 100 innings (127 pitchers)
Junk’s ERA in 2025 was 4.17, which was 1.03 runs higher than his FIP. That’s FIP’s 17th biggest underachievement in the league (again, at least 70 innings). But many pitchers with bigger holes downright stunk and had huge ERAs. If you look at FIP as a percentage of ERA, Junk was in the bottom 10; his FIP was 75.4% of his ERA.
Now xERA, which measures the quality of contact, was much less sympathetic. By that metric, Junk actually outperformed his ERA by about 6%. Of the 18 pitchers with the lowest FIP/ERA ratios last year, Junk is the only one with an xERA higher than his ERA.
That table above is why.
And yet his xERA was 4.45. A pitcher with a top-10 contact rate and a top-10 EV90 should have an xERA that you can only count with two hands. The only qualified hitter in the top 10 in EV90 last year who was even in the top 50 in contact rate was Vladimir Guerrero Jr.
So why didn’t Junk make the opponents look like Vladito?
Two reasons. First, in addition to not walking anyone, Junk did one thing very well in 2025: He got batters to chase. Did he make hitters swing and miss on pitches outside the zone? Oh no, of course not. Junk’s out-of-zone whiff rate was worse than the in-zone whiff rate of 20 different pitchers.
But even if you hit the ball, it’s difficult to do much damage on pitches outside the zone. The league-wide wOBA on balls batted outside the strike zone was .285; inside the zone it was .381. A healthy 19.8% of balls put into play against Junk came on pitches outside the strike zone, which was in the top third of the league. And here I think he got unlucky; Junk allowed the highest wOBA in baseball (minimum 300 total balls in play) on pitches outside the zone, surpassing his xwOBA by 80 points.
The second thing that went well for Junk was that he used the entire ballpark.
LoanDepot Park is a pitcher-friendly stadium. Using Baseball Savant’s xHR, the sizes of Kauffman Stadium and Busch Stadium alone would have led to fewer home runs than Junk’s actual home park. If he had to give up the same batted balls at Citizens Bank Park, Junk would have allowed seventeen home runs instead of eight:
That’s a huge red flag for regression.
I think Cabrera is far from the ace-in-wait that certain individual pitches make him seem. I’m not a big Weathers fan either. And whatever else you want to say about Junk, it’s a developmental triumph that the Marlins got even one season like 2025 from a guy who took until age 29 to establish himself as a big league player. (As I was writing this, Junk turned 30 on Thursday. Many happy returns.)
But the Marlins have now lost enough rotation depth that they are interested in the Quad-A guys and prospects. Junk’s command and Yesavage Lite’s attributes make him a pitcher worth keeping an eye on, but given the choice between believing in his FIP and believing in his xERA, I have to choose the less flattering of the two.
#Janson #Junk #declining