Since returning from the disabled list (neck nerve impingement), Stephen Strasburg’s fastball velocity has dropped from averaging 96.1 mph to averaging 93.9 mph. For a pitcher known for bringing the heat, the decline immediately impacts his value going forward. The question isn’t if but how much will be the decline.

First, I completely understand Strasburg could get his fastball velocity back as soon as his next start (the chances for this could be another whole article). When determining the 30-year-old righty’s value, I needed to plant a flag at some velocity and then come up with a projection.

For reference, the following table has his stats before and after coming off the DL. I’ll ignore his July 20th start in which he missed a month before and after it.

Strasburg’s 2018 Stats Before & After the DL Fbv FB% SwStr% Zone% K% K%-BB% Siv SI% xFIP Before DL 96.1 45.0% 11.6% 49.9% 29.1% 23.2% 95.6 5.5% 3.00 After DL 93.9 39.1% 12.3% 43.8% 25%% 16.2% 93.0 13.8% 3.49

Besides the swinging strike rate, Strasburg is performing quite a bit worse after coming off the DL. The two main signs of an injured pitcher are front and center with the velocity and Zone% decline.

It may seem like Strasburg is moving away from a fastball but he’s not. While his four-seamer rate has dropped, his sinker usage has increased from 6% to 14%.

While a 3.49 xFIP seems reasonable with the velocity loss, years of data exist on Strasburg’s fastball. The results can be verified.

Using data from 2015 to present, his fastball results can be compared at different velocities using pERA (pitch ERA). With pERA, each pitch is given an ERA equivalent value based on its groundball and swinging-strike rate. His fastball’s pERA can be combined with his other pitches pERA to get an estimated ERA.

Strasburg’s Fastball Effectiveness mph Pitch pERA GB% SwStr% Cnt Pitch pERA GB% SwStr% Cnt 92 FF 5.77 22% 3% 29 SI 4.94 41% 10% 40 93 FF 5.51 32% 7% 112 SI 3.76 60% 10% 84 94 FF 4.80 38% 13% 464 SI 4.86 42% 14% 59 95 FF 4.51 28% 14% 711 SI 3.53 50% 28% 43 96 FF 3.90 34% 17% 841 97 FF 3.83 37% 15% 381 98 FF 3.29 35% 16% 75

With his four-seam fastball, there is a steady improvement as his velocity has increased. His overall ERA doesn’t move in-step with the fastball ERA as his other pitches, which usually have better results, should continue their production.

For an example, when his fastball velocity drops from 96 to 94 mph, his pERA increase by 0.90. Assuming a 45% fastball usage, his ERA should be expected to jump by 0.41 (45%*0.90). It’s just about the same as his xFIP increase.

The sinker adds a little wrinkle to the discussion. The main issue with the sinker is that he’s just not thrown it much. With the limited usage, its results bounce around quite a bit. Grouping them all together, the sinker’s pERA is 4.35 though supported by the 28% SwStr% at 95 mph. The sinker may be a better pitch for him at lower velocities as it has more time to sink if he throws it 100% of the time.

Going back to our pre-season Depth Chart values, Strasburg (25 NFBC ADP) was projected at 3.31 ERA. By bumping his ERA projection up to 3.72 (3.31+0.41), his ERA projection would have been like those of David Price (3.67 ERA, 103 ADP), Marcus Stroman (3.72 ERA, 151 ADP), Jon Lester (3.73 ERA, 116 ADP), and Blake Snell (3.75, 196 ADP). With no velocity rebound, he should be drafted in the triple digits. The potential for a bounce-back exists so his ADP will be between the 25 ADP from last season and the 100’s.

I ran a quick poll right before posting to get a reading on Strasburg’s popularity.

What do you think Stephen Strasburg's ADP (25th in 2018) will be next season if his velocity doesn't bounce back by season's end (assume no spring velocity readings available)? — Jeff Zimmerman (@jeffwzimmerman) September 4, 2018

Most owners, 60% at the time of publishing, still see him valued him as a top-75 pitcher.

One problem I have is that Strasburg had Tommy John surgery, continues to go on the DL, and is in his 30’s. He has more indications of a breakdown than a breakout. There is a decent chance we could have seen Strasburg’s best season. Or not. No one knows for sure.

Strasburg’s fastball velocity loss could hamper his performance, but it seems like owners are valuing him on his upside or don’t understand the possible downside. If the season ended today, he’d be one of the most debated players this offseason and I’ll probably not own him in any leagues.