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Is Michael Bourn About to Decline?

Michael Bourn is the best free-agent left on the market. The main reason Bourn is still out there has to do with the market. After the other big-name outfielders signed, there were no teams left on the market who could offer Bourn a mega-deal. The only team he’s been linked to recently is the Mets, who are only interested in adding him if MLB decides to exempt the Mets from giving up the 11 pick. But even if the Mets signed Bourn, they would want him to lower his demands. The team doesn’t want to invest a five-year deal in a player so dependent on his legs, figuring, once the speed goes, Bourn will no longer be useful. The general notion suggests that players like Bourn fall off a cliff as their speed declines. But is Bourn the exception to that line of thinking?

In order to find similar players, I tried to find guys that utilized the same approach at the plate, at the same point in their careers. In order to find the players who were mostly dependent on speed, I sorted by stolen bases. The biggest problem here is that stolen bases is a counting stat. In order to get a better idea of the most frequent runners, I took plate appearances over that period, and divided by the number of steals. This gave me a nice rate stat I could use to compare players. From there, I grabbed the players who had a PA/SB rate of 30 or lower. This initially gave me a list of 34 players, including Bourn. For the purpose of looking at how Bourn would perform going forward, I had to remove all the current players on the list that haven’t hit age-30 yet. That bumped the list down to 28 players.

So, let’s assume Bourn has to settle for a three-year deal. If that’s the case, we can try to look at these players, and how they performed through their age-32 years. This is where we start to see a troubling trend. Fifteen of the 28 players saw their PA/SB rates fall below 30, which would have pushed them off the first list. Here’s a breakdown of how these players fared as aging kicked in.

PA/SB age 30-32 Players %
Major decline (over 30) 16 59%
Decline (lost > 4 PA) 2 7%
Same (within 4 PA) 5 18%
Better 4 14%

Fifty-nine percent of those players declined enough to not meet our initial threshold of one steal per 30 plate appearances. Seven percent saw a significant decline, but stayed within our threshold. In total, 32% of the players either stole bases at the same rate, or actually improved on their totals.

What if Bourn actually gets the five-year deal he’s looking for, though. When we sort that list to include how those players performed during their age-33 and age-34 seasons, things start to look pretty bad. The list drops to just 16 players, only eight of whom received 600 plate appearances over those two years. Outside of Fred Lewis, who had to be excluded because of age, 10 other players failed to see a major league plate appearance after their age-32 season. Of the 16 remaining players, 10 more fell below our 30 PA/SB threshold.

PA/SB age 33-34 Players %
Major decline (over 30) 20 77%
Decline (lost > 4 PA) 2 8%
Same (within 4 PA) 4 15%
Better 0 0%

Those last two seasons were tough. Seventy-seven percent of players saw a huge decline in their stolen base rates, and an additional eight percent saw a big decline. Only 15% of the remaining players were able to continue stealing bases at a similar rate at this point in their careers.

Overall, those numbers don’t bode well for Bourn. If there is a silver lining, however, it’s that the players who were able to maintain or improve on their stolen base rates over the next three seasons were the ones that received a lot of playing time. That does give some hope that Bourn might lucky enough to maintain his skills over the next three years. Giving Bourn a five-year deal would be a tough pill to swallow. The decline rate for these players is high enough in their early thirties, but it really jumps once they hit 33 or 34. Bourn had the most stolen bases of any player included in this study, which is another reason for optimism, at least in the short run. But the risk with speedy players is very real as they get into their 30s. The Mets are wise to be cautious in this scenario.