Jarrod Dyson and Outfield Sprint Speed Aging

Based on media reports, the Orioles have been in communication with Jarrod Dyson, a fleet, left-handed outfielder who has excelled everywhere in the outfield.  The communication raised to a level that was serious enough for the Orioles to consult his medical files and find them to be supposedly unconcerning.  For several of us at the Depot, this is some good news.  Dyson was a major element of several of out plans for the offseason and a piece that I have thought fits the club well.  He provides speed, a good on base percentage, and a solid backup option to Adam Jones (and a potential solution in 2019 when the club might be Jones-free).

He has a couple major drawbacks.  First, he cannot hit southpaws.  This means that he can be a heavy component of a platoon (most pitchers are right-handed), but he is a liability to late inning relievers and is largely restricted to defensive replacement duty when a left hander starts on the mound.  He has been a very effective pinch hitter with a 134 wRC+ (over 24 PAs).  Second, he is getting into his twilight baseball years and will begin next season in his age 34 season.

While my preference would be a two year deal, I recently noted that I would be fine securing Dyson to a three year contract.  This resulted in a flourish of tweets telling me I was paying too little attention to his age and that my perspective was rooted too much into his defense, which was benefited by his speed.  To some extent, the narrative holds true when we look at his position based UZR/150s (runs saved):

Age	Sprint (ft/s)	LF	CF	RF
31	30	25.2	18.2	11.2
32	29.6	29	19.6	35.5
33	28.8	19	8.6

Dyson's defensive performance was otherworldly in his age 31 and 32 seasons.  However, he suffered a major decline in speed this past season.  The optimist would suggest that his hyperextended toe resulting from a July 22nd wall crashing and a sports hernia that was diagnosed August 19th led to his decreased speed and that we should expect a return to form with a healed hernia.  That optimistic view notes that speed tends to change mostly due to body morphology changes or accumulated hamstring and back injuries.  Toe injuries can be death, but it appears he has recovered from that and hernias tend to mend well.  Neither of these look like a chronic issue.

Edit: In the comments someone succinctly noted that I am not appropriately communicating the outcomes for sports hernias.  I will walk through the process. Before the article was posted, I did some research. Only player I found to have repeated sports was Scott Posednik who underwent five surgeries in the span of about three years.  It is uncertain to what extent that impacted him as he was still fairly fast, but less disruptive which may be due to a lingering groin issue or simple aging.  From there, I ask a person I went to school with who performs surgeries like this. He said that basically everyone is fine and able to compete in three months and that recurrence was rare, maybe 5 percent.  After getting the comment below, I sought him out again and he said that to suggest a sports hernia is a serious injury feels to him to be a rather outdated perspective and perhaps the individual is not current with modern therapies. However, he said that while he performs surgeries that he is not much involved in the rehabilitation process and follow up.  So...I contacted a friend of mine who works for an MLB team on their medical staff and is experienced with bringing players back from all sorts of injuries.  He stated that sports hernia surgeries are a very successful procedure with few recurrences.  He did not have a number on hand, but said that it has to be less than 10%.  After all of this, I have concluded that my original text is accurate and the commenter did not have a complete understanding of the outcomes for, at least, this demographic.

Overall how does speed change in outfielders as they age?

Using sprint speed data from 2015-2017 for outfielders, I was able to construct the following table.

Age	Sprint Change (ft/s)	Example	>28 change	Example
22		28.00
23	-0.03	27.97		30.00
24	-0.12	27.85	-0.05	29.95
25	-0.06	27.79	-0.02	29.92
26	-0.05	27.73	0.02	29.94
27	-0.09	27.65	0.01	29.95
28	-0.08	27.57	-0.03	29.92
29	-0.10	27.47	-0.04	29.88
30	-0.12	27.35	0.00	29.89
31	-0.10	27.25	0.10	29.98
32	-0.11	27.14	0.08	30.06
33	-0.11	27.03	0.03	30.09
34	-0.06	26.97	0.15	30.24
35	-0.14	26.83
36	-0.11	26.72

What the table shows are two situations.  The second and third columns explore what happens to the population in general in terms of how speed changes from one year to the next as well as what happens to an age 22 runner who sprints 28 ft/s as he ages.  The second take a subgroup out of that population to see what happens to plus runners (>28 ft/s) as they age with a value that is more like that value (30 ft/s) for a 23 year olds starting point.

What the data appears to indicate is that the population of outfielders in general see their speed degrade with time.  Someone in Dyson's situation would be expected to lose about a third a foot per second as he aged over a three year deal when fit to that model.  If we assume that 28.8 ft/s is his real talent level, then that would be a 28.5 ft/s.  That would have made him tied with the fastest Oriole on the roster in 2017 (Craig Gentry).

For the faster group, the data does not go as far.  I did not feel comfortable extrapolating out to where I did not have five or more data points to consider, so the results above would only consider Dyson's first year.  What I find interesting about the results though is that elite runners tend to remain elite runners.  In other words, if you have a body type that is fast then you tend to remain fast.  We see this pretty often that while world class sprinters tend to peak in their mid to late 20s, but they retain that speed into their late 30s.  True, they rarely challenge for medals in their late 30s, but they only lose a stride or two over several years.  That means a great deal on the track, but perhaps not as much out on the ball field.

So, sure, maybe offering a three year deal to a speedster entering his mid thirties is something that should be avoided, but I still think the gamble is fine.