Julian Merryweather's Tumbling Velocity Could Spell Long-Term Trouble

It was just two seasons ago when Julian Merryweather was arguably the most valuable relief pitcher on the Cubs. After an injury marred 2024 season, his performance in 2025 has been subpar, to say the least.  His more recent struggles came to a head this past week, when he posted back-to-back two-run outings against the Mets and Marlins. Is there any reason for fans to panic about the veteran right-hander?

In short, yes. Entering Saturday’s action, Merryweather’s 4.76 ERA is actually better than his 5.20 xERA, and right on par with his 4.75 FIP. Both of those numbers would suggest that he has been as bad as his ERA would indicate. 

Let’s take this one step further. Why has his performance suffered? The first and most obvious place to look is in his strikeout rate. In the 2023 season, Merryweather struck out 32.3 percent of the hitters he faced, which was 16th in baseball among 162 qualified relievers, according to FanGraphs. This year, his strikeout rate has plummeted to 18.2 percent, which is 147th out of 188 qualified relievers. 

Merryweather succeeded in 2023 with a simple approach. He had two plus-pitches, a four-seam fastball and a slider, that he was capable of throwing in any count, in any situation. The fastball at the top of the zone tunneled well with the slider at the bottom of the zone. 

With the fastball averaging 98.1 mph two seasons ago, you had to be ready for that while also protecting against the slider, thus creating swing and miss with the breaking ball. Here’s his performance on each pitch from the 2023 season, compared to this season, and I trust you can spot the differences. All stats courtesy of FanGraphs:

Hitters still, mostly, can’t hit the slider well. They’re just chasing less, and as a result, swinging and missing at it a whole lot less. This is probably due to the two mph decline in velocity across the board. Hitters have a fraction of a second more to decide if the pitch is a slider or a fastball out of Merryweather’s hand, and that fraction of a second is making all the difference. 

Within that vein, I have good and bad news. His velocity has been slowly declining all season, with both his fastball (94.8 mph) and slider (83.7 mph) velocity hitting a season low in his outing against the Marlins last Tuesday. Frankly, I expected we’d see an injury list placement after that, but instead we have good news: he rebounded to average a season high 97.2 mph on the fastball in his scoreless outing against the White Sox on Friday:

In 2019, Driveline Baseball found that adding one mph to a player’s fastball velocity could be worth as much as .25-.35 in WAR in one season. In 2023, Julian Merryweather was worth 0.8 WAR on FanGraphs. Applying this logic, him losing two mph on his fastball might cost him just about all of his value, and that sure is what it feels like at this point. 

For now, let’s hope that the added velocity in his most recent appearance is a sign of more things to come. Otherwise, there might not be much good weather on the North Side when Julian Merryweather comes into the game.