Royals lose Danny Duffy to the IL

The left-hander has a left forearm flexor strain.

The Royals were days away from getting healthy. Kyle Zimmer and Jesse Hahn are on rehabilitation assignments in Triple-A. Their return will fortify a bullpen that has, at times, been exposed for a lack of depth over the last few weeks. Adalberto Mondesi is joining the relievers in Omaha this week. His return is likewise imminent and will shore up both the lineup and the defense. Things were looking up in Kansas City.

Not so fast.

On Monday the Royals announced they would be skipping Danny Duffy’s scheduled Tuesday turn in the rotation. He was not either of the listed starters for the upcoming series against the Milwaukee Brewers.

Later on Monday, the club announced Duffy would hit the IL with a left forearm flexor strain. There is no timetable for his return.

This is just awful news for a team so close to getting their squad back to full health. Duffy was, hands down, the best starter on this staff. Heck, he was among the best starters in baseball over the first quarter of the year. With a rotation that is depending on a combo of young arms and veterans (is it OK to refer to Brad Keller as a veteran?) Duffy had emerged as a stalwart. Originally penciled in as the number four starter behind Keller, Mike Minor and Brady Singer, Duffy shoved his way past the other arms and quickly established himself as the pacesetter in the rotation. Finally, he’s the unquestioned leader.

In the final year of his contract, Duffy was enjoying something of a late-career renaissance. He was striking out batters at a rate of 28.2 percent, the highest of his career for any season. His walk rate had dipped to 7.1 percent, the lowest of any season since his 2016 return to the rotation on a full-time basis. His K-BB% which is basically the difference between his strikeout and walk rates is an impressive 21.2 percent. It’s the second time in his career he’s been above 20 percent, the other coming in 2016.

In 41.2 innings, Duffy posted a 1.94 ERA, a 3.75 xFIP and a 46 ERA-. (This is a measure of ERA adjusted for park and league and scaled to 100. Anything below is better than average. Duffy has been 54 percent better than league average.) Included in his 2021 season was his 1,000th career strikeout. Wearing number 30, it featured a little Yordano-esque flair.

To this point, Duffy had made just seven starts. That’s about a quarter of the season, so there was a long way to go and there was no guarantee he could keep that performance going through an entire season. His HR/FB rate is abnormally low, leading to a 0.43 HR/9. His strand rate of 81.4 percent is about six percentage points above his career average. Duffy was most likely going to give back some of those gains at some point during the summer. But aside from the depressed home run rate, there isn’t really an indicator that suggests regression was lurking around the corner.

Spinning his way to success

All of Duffy’s pitches this year have increased spin.

As you would imagine, the more spin, the more movement. His sinker and change have a little more rise than usual. His secondary pitches have a load of extra downward vertical movement.

This has positively impacted his contact rates. Batters are swinging at about 67 percent of the pitches Duffy delivers in the zone. That’s about the usual rate for him. Those hitters are making contact on only 78.4 percent of those swings, well off the league average of 82.1 percent and Duffy’s career rate of 81.5 percent.

And the extra movement is also causing hitters to expand the zone against Duffy. His chase rate is 31.6 percent, his highest rate of the Statcast era.

So while there were some indicators that Duffy’s excellence wouldn’t continue at a pace of what we’ve seen over his first seven starts of 2021, there wasn’t a massive flashing red light trying to alert us that a massive regression was ahead. The increase in spin and movement would make sure of that.

It’s not just about the spin. Duffy, as you know if you’ve been reading this newsletter for any length of time this season, is throwing harder than at any point since he returned to the rotation full-time in 2016. His fastball (four-seam and sinker) velocities are up an average of 1.6 mph. His offspeed offerings are up an average of 1.1 mph. And his breaking pitches are coming in extremely hot, up an average of 2.3 mph.

It almost feels like I’m burying the lede, bringing up Duffy’s velocity bump so late in this issue. It’s the most obvious change from the previous incarnations of Duffy we’ve seen to the current pitcher. Indeed, almost every gain he’s made (both spin and production) have flowed from this bump in velocity.

While an increase in velocity can come with an increase in positive results for a pitcher, it can also lead to increased injury risk. His overall velocity on the fastball wasn’t down in his last start last Wednesday. Duffy’s overall fastball average of 93.9 mph was tied for his second-highest in a game in 2021, there was a noticeable dip between the third and the fourth inning.

The slowest fastball he threw in that start came on his first one of the fourth inning. This is not some sort of “ah-ha!” moment, where it’s obvious an injury occurred. He was still able to touch 95 mph as he progressed in his start. And the fastballs he threw after delivering his 22nd of the night averaged 93.5 mph. Duffy’s velocity chart in his last start actually mirrors his velocity chart from most of his starts. He’s a guy who comes out bringing almost max effort. His velocity tends to diminish as he goes deeper into games. This isn’t unusual. But it appears Duffy worked this offseason in building up the strength to maintain that velocity. He’s done a really fine job of doing that in most of his starts.

Duffy’s velocity chart from his May 6th start against Cleveland was interesting. There are three distinct “sections” on the velocity of his fastball.

The sudden decrease in velocity doesn’t concur with the start of a fresh inning, but when Duffy had unleashed a slower fastball early in the game, it portended an overall decrease in velocity. At about the fourth inning he settled into somewhat of a groove before amping up and finishing strong in the sixth. The second and sixth innings in that start carried the highest stress for Duffy.

Again, there’s no “silver bullet” injury pitch. Nothing from what we’ve seen would indicate that Duffy was either carrying an injury or had a specific pitch where it occurred. Duffy threw 100 pitches in his last start. He was at 107 in each of his previous two prior to that. It could just simply be that the increase in velocity coupled with workload eventually wore him down.

Medical info I learned when I used Google

It’s important to note that a strain isn’t just a pulling of the tendons where it’s stretched just a little too much. A forearm strain is an actual partial or complete tear of the small fibers of the forearm muscle. There are three grades of strain, so until we hear the definitive word from the Royals, it’s all speculation about how much time Duffy will miss. A Grade 1 strain is the mildest and involves no loss of strength. Grade 2 is characterized by a loss of strength and some significant pain. A Grade 3 strain is a rupture that requires surgery to repair.

According to a study published in the Orthopedic Journal of Sports Medicine in 2017, the average time on the IL for a major league pitcher with a forearm flexor injury was 42 days. The study covered the 2010 through the 2014 seasons. It was also discovered that 19.4 percent of those pitchers who had a flexor injury required UCL reconstruction (i.e. Tommy John surgery) within 365 days of sustaining the injury. They did not note if it was more or less common if the pitcher had already undergone a Tommy John surgery.

So it sounds that while a second Tommy John isn’t something that is the guaranteed or expected outcome from this injury, it is likely Duffy will miss at least a month, depending upon the severity.

Impact on the rotation

Kris Bubic, who we all assumed would be replacing Daniel Lynch in the rotation, will make the start in Duffy’s place on Tuesday. Brad Keller will take his normal turn on Wednesday. The Royals are off on Thursday and again on the following Monday which gives the schedule some serious opening week vibes. So many off days. So if there was ever a time to lose a key starting pitcher, maybe it’s now. The Royals could go with a four-man rotation for the next week and a half or so.

The Royals have been casting around for a fifth starter. Now they need to replace their best starter. And there’s no guarantee that when Duffy returns to the rotation (if he returns) that he will be as effective as we saw in April and early May.

Injuries are never good, but with Duffy and everything he’s been through to get to this point where he was having an outstanding start to his season, is extremely disheartening.

Central issues

• White Sox 16, Twins 4

Hug a Twins fan. Or don’t. It’s a free country. Better yet, just enjoy the glory of Yermín Mercedes swinging on a 3-0 pitch from Willians Astudillo that was delivered at 47 mph.

• Cleveland 4, Angels 7

Shohei Ohtani hit his league-leading 13th dinger and drove in three to lead the Angels past Cleveland. He’s scheduled to start against them on Wednesday. You should probably buy the MLB TV package just to watch this guy.

• Detroit 4, Seattle 1

Casey Mize threw 7.2 innings of three-hit ball, striking out seven. Eric Haase hit a pair of homers and Jonathan Schoop added a two-run shot for the scoring.

For whatever reason, I can’t get the standings to load this morning. Just know the Royals are still in third place in the Central, seven games behind the White Sox.

Up Next

The Royals open a brief, two-game series against the Milwaukee Brewers. It’s Bubic against Chris Woodruff. First pitch is at 7:10.