Monday, October 26, 2015

A (Somewhat) Unusual Aspect of Daniel Murphy's Postseason Home-Run Streak

As we approach the opening of the 2015 World Series on Tuesday night, the dominant story line has been the home-run streak of Mets second-baseman Daniel Murphy. He has hit a home-run in each of his last six games, a playoff record.

One of the key principles I've gleaned through nearly 15 years of hot-hand research is that long streaks are most likely to be achieved by players and teams with very high baseline success rates.

The late Harvard paleontologist Stephen Jay Gould famously wrote that, "Long streaks always are, and must be, a matter of extraordinary luck imposed upon great skill." Thus, if you look at some of longest streaks in American sports history -- 88 straight wins by John Wooden's UCLA men's basketball teams of the 1970s, and 90 by Gino Auriemma's UConn women of the 2000s; Joe DiMaggio's 56-game hitting streak; and Tiger Woods making the cut in 142 straight golf tournaments -- these are all athletes and teams that generally succeeded an enormously high percent of the time. Throw in a little luck to avoid a loss in a close game (or a hitless game or missed cut) and, voila, you have a long streak.

Murphy, however, does not have a high base rate of home-run production, never hitting more than 14 in any of his seven regular seasons, and averaging about nine per year. A home-run streak by Murphy is therefore more out-of-the-ordinary than, say, one by Mike Trout would be. (Click here for a statistical analysis taking this approach.)

A second unusual feature of Murphy's streak -- and perhaps I'm being too picky -- is that, when a player goes on a monster home-run tear, there's a good chance he'll have one or more multi-homer games within the streak. Murphy has not, hitting exactly one homer per game during his streak.

In September 2010, for example, then-Colorado shortstop Troy Tulowitzki hit 14 home-runs in a 15-game span, including four multi-homer games. (Playing at homer-friendly Coors Field for many of those games probably helped.)

Then there's the case of Hee-Seop Choi, whose brief MLB career included a weekend in June 2005 in which, playing for the Dodgers he belted six home-runs in a three-game series vs. the Twins (two, one, and three homers, respectively, on Friday, Saturday, and Sunday). He hit only three more homers the rest of the season and never played in the majors after 2005.

Finally, when we look at the players Murphy surpassed for most consecutive postseason games with a homer, the tendency for multi-homer games to be embedded within the streaks is there (highlighted in yellow). The number of homers a player hit in a given game are shown in parentheses. Click on the number in parentheses for the box-score.

Carlos Beltran, 2004, 5 straight games: NLDS Game 5 (2); NLCS Game 1 (1); NLCS Game 2 (1); NLCS Game 3 (1); NLCS Game 4 (1)

Evan Longoria, 2008, 4 straight: ALCS Game 2 (1); ALCS Game 3 (1); ALCS Game 4 (1); ALCS Game 5 (1)

Jim Thome, 1998-1999, 4 straight: '98 ALCS Game 5 (1); '98 ALCS Game 6 (1); '99 ALDS Game 1 (1); '99 ALDS Game 2 (1)

Juan Gonzalez, 1996, 4 straight: ALDS Game 1 (1); ALDS Game 2 (2); ALDS Game 3 (1); ALDS Game 4 (1);

Jeff Leonard, 1987, 4 straight: NLCS Game 1 (1); NLCS Game 2 (1); NLCS Game 3 (1); NLCS Game 4 (1)

Reggie Jackson, 1977-1978, 4 straight: '77 WS Game 4 (1); '77 WS Game 5 (1); '77 WS Game 6 (3); '78 ALCS (1)

Lou Gehrig, 1928-1932, 4 straight: '28 WS Game 2 (1); '28 WS Game 3 (2); '28 WS Game 4 (1); '32 WS Game 1 (1)

Don't get me wrong. Hitting one home-run in each of six straight games, as Murphy has done, is amazing. It's just that, if a player is seeing pitched balls really well or concentrating better than ever, wouldn't we expect such a mental state of being "in the zone" to manifest itself within the same game?

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