Busted Batters’ Backs Are Bad

Several high-profile hitters have been slowed by back injuries this season. The Yankees’ Kevin Youkilis is on the disabled list with a sprained back for the third time in his career. Shane Victorino missed eight games from late April to early May because of a bad back. Jose Bautista missed about a week of play with back spasms. When back problems occur to hitters, fans should not be surprised to see a marked loss of future production from those players.

I have always considered back injuries to be one of the worst injuries a position player can have. The fear probably stems from following Mike Sweeney when he was with the Royals. He continued the tradition with the Mariners, where he went on the DL for back injuries twice. In all, Sweeney landed on the DL seven times for back injuries.

To figure out the exact effects of back injuries, I went back and compared the players’ stats of the season before the injury, year of the injury and the next season. One item to remember when looking at the values is survivor bias. Players whose backs are really messed up will have less of a chance of returning and putting up horrible numbers.

I took all players who spent time on the DL for a back injury between 2002 and 2011. In all, I examined 136 DL stints for this sample. Only 10 times did a player go back on the DL during the same season for a bad back. The batters averaged 48 days per DL trip. Some of these stints would have overlapped the start or end of the season, so the actual average is probably much higher. Additionally, 22% of the players ended up on the DL in subsequent seasons for a back injury.

In addition to comparing the previous season’s stats, the DL stint year and the year after, I also looked at the stats before and after the DL stint for the year in question (if possible). Finally, I looked at the statistical change from the first time a player went on the DL. I figured once they had a bad back, they would always have it.

All right, here are the numbers:

Year-1: Year before DL stint
Year: Year of DL stint
Year+1: Year after DL stint

Overall, the results are pretty discouraging. On average, a player will see his OPS drop by 50 points for any DL trip due to a back injury from the year before to the year after the stint. If it is a player’s first time, the drop is 73 points. The main item taking a hit was the player’s power, with SLG and therefore ISO leading the decliners.

The one interesting note was the player basically getting the same production before and after the injury during the season. The values were all over the place, some much higher, some lower. It seemed the players were split in going on the DL too late or coming back too early.

For a comparison, here is how Kevin Youkilis performed the year before, during, and after his first back DL stint in 2011.

Since his first back injury, Youkilis’ production is down over 200 OPS points. Besides the drop in production, he has not been able to stay off the DL for his back. In the two next seasons, he was placed on the DL for his back. A bad back is just sapping what production Youkilis has left in him.

While back injuries are not even close to being the most common hitter injury, they probably are one of the most devastating. The players in question significantly drop down to a new production level, and fans should rarely expect a player to perform at previous levels once he busts up his back.