Howard has had big drops in his OWP the last 2 years. OWP or offensive winning percentage is a Bill James stat that says what a team's winning percentage would be if it had a lineup of 9 identical players who all hit alike and they gave up an average number of runs. Since I got the data from the Lee Sinins Complete Baseball Encyclopedia, it is park adjusted. Here are Howard's OWP for each of the last 3 seasons with his age in parantheses:
So the declines are .102 and .093. For players who had long careers, such big back to back drops in OWP are somewhat rare, especially for someone under 30. Some stories I read using google news search indicate he is in better shape this spring and is hitting better than usual this pre-season. So maybe he has taken the necessary steps to stop the decline.
To see how unusual his declines are, I used a list of players that I have compiled before. This list includes all players who had 15+ seasons with 400+ plate appearances from age 20-40. Then I found all cases of players having back to back seasons of a drop in OWP of .075 or more. The tables below show all of these cases (more discussion of the tables below).
There are 22 such cases. But in only 3 of them, did the fall in OWP start before the age of 30. Those belong to Robin Yount, Jake Beckley and Mickey Vernon. Beckley's started at age 23 and neither of my biographical encyclopedia's mention anything. Same for Vernon's decline. Yount had shoulder problems during the 1984 and 1985 seasons and actually had surgery twice. But both Beckley and Yount are in the Hall of Fame. So if Howard can end up with 15+ seasons with 400+ plate appearances he has a 2 out of 3 chance of making the Hall of Fame.
If I had limited the study to declines of .093 or more, there were only 8 guys. The only one whose decline started before age 30 was Vernon. So who knew that he had something in common with Howard?
In the tables below, the numbers in red are the decline years. The year before the decline is there for each player for reference. Two guys had 3 straight years that fit the criteria. They were Jimmy Dykes and Willie Keeler. Yount and Honus Wagner had two such streaks. The average age at which the decline started was 33.95. 17 of the 22 cases started at age 33 or older.
There were 91 players with 15+ seasons with 400+ plate appearances and 22 back to back seasons of a drop in OWP of .075 or more. So nearly 25% of the 91 players had these big back to back declines. That makes it look like what has happened to Howard is not that rare. But what is rare is the age at which it has happened to him.
What happened to these guys in the third year? Did they finally rebound? Well, we know that Keeler and Dykes each had declines that fit the criteria in the third year. 5 players did not get 400+ PAs the next year. The average change in the third year, including Keeler and Dykes (who were the only declines), was a positive .078. 8 of the 17 had changes of +.100 or more. So Howard has a good chance to bounce back but also has a chance not to make it to 400 PAs. Mickey Vernon improved .295 in the third year.