More Than You Wanted to Know About Shared Birthdays in MLB

So tfloyd sent me down a rabbit hole on Wednesday. Teams with players with shared birthdays. This required a lot more programming than I expected, but the extra work will hopefully pay off by making similar analyses easier in the future. But here we go.

I presume you’ve all heard of the Birthday Problem. The birthday problem states that if all birthdays are equally likely, then in a random group of 23 people it is just better than 50-50 that two people in that group will share a birthday. I’m not going to go into the math of that, there are about 2.35 million Internet sites that will explain it, and it’s not important for our purposes for a number of reasons.

First, all birthdays aren’t equally likely. February 29th for example, is really unlikely. Big holidays are somewhat less unlikely because people who can schedule induced deliveries avoid holidays. There are also some age cohort effects, in which particular dates (like July 31st in the US), serve as boundaries for Little League ages and those who are almost a year older than other kids have a marked advantage early on in their level of competition, which might translate into, say, August US birthdays creating more professional baseball players. Not going to measure that effect either.

Second, while baseball teams are within shouting distance of 23 players, an actual roster over a season has a lot more players than that, so that the effective birthday number creates much higher probabilities that two players on a team at some time in a season will share a birthday. I have data on 18.796 players who between them played on 2.554 teamsm and only 410 teams failed to have a shared birthday at any point in the season.

The Record Holders

Five teams had four players who shared a birthday:

tfloyd identified the Braves high-water mark with three players sharing a birthday. Steve Avery, David Justice and Greg Maddux, April 14th babies all, played together in 1993, 1994, 1995 and 1996. But they weren’t the only triplets. There’s also JC Boscan, Omar Infante and Mike Minor, all of whom were day-after Christmas deliveries,

Sure, But Who Was The Best?

tfloyd noted that Maddux + Avery + Justice was a pretty awesome birthday trio. And in fact, they are the highest-WAR trio of all time. In 1995, they combined for 14.91 WAR; 14.61 in 1993 is the second-best mark and 13.84 in 1994 is the third best mark for birthday triplets. In fourth place is Steve Carlton (10.14) Lonnie Smith (2.27) and Orlando Isales (0.07) for the 1980 Phillies, coming in at an aggregate 12.48.

Among birthday twins, the most potent were Bill Freehan (6.92) and Dick McAuliffe (5.58) for the World Champion 1968 Tigers. So, to answer tfloyd’s question there were no other completely awesome threesomes, but a darn good duo in Detroit. Fergie Jenkins in his incredible (11.76) 1971 season had a minor addition from his birthdate mate, J.C. Martin (0.23) for second place.

And, on a Personal Note

Tom Glavine is exactly ten years younger than me. (Happy 60th, Glav!) While my WAR numbers are 0, I think Glavine, Elton John (9 years older) and I make a pretty good threesome, including two Hall of Famers. I am the Orlando Isales of that group. And on a second personal note, my mother turns 92 in a couple of weeks. She shares a birthday with Old Scrap Iron, Phil Garner, who passed away this week. Happy birthday, Mom, and RIP Phil. (Also RIP to ACHE, Garret Anderson, who passed away today at 53.)

Now to the Game

The Phillies started Taijuan Walker, who is not having a good start to the season and the Straits of Taijuan continued tonight. He couldn’t find the plate; throw in a couple of singles and it was 2-0 before 7 pm. Four more runs in the second inning, capped by a 3 run homer from the light-hitting Austin Riley. I suspect there is nothing wrong with Austin Riley’s swing that facing lousy pitching can’t cure. Yet another homer from Folk Hero™ Dom Smith in the 3rd and Walker’s ERA had climbed from 7.36 going into the game to 9.68.

I implied last week that Martín Pérez might have made one of his last starts for the Braves. I was starting to look prescient as he was released shortly after the game. But he chose to take the assignment to Gwinnett rather than free agency and is back starting with the parent club six days later. He lost that game 6-0 but was leading 6-0 when he took the mound at the start of the 2nd. He didn’t pitch a lot better than Walker, to be honest, but got timely outs in the exact circumstances in which Walker had timely non-outs.

After that, hibernation by both teams. At least, I had to assume hibernation, since I fell asleep (it’s been a long week.) I awoke for the top of the 8th, just in time to a Michael Harris II homer off Orion Kerkering, who I was surprised to learn was still allowed in town after hisend to the 2025 Phillies season. I looked back in the box score: Pérez went 7 6 and it turns out Walker pitched a clean 4th to lower his ERA to 9.16. If anything reportworthy occurred in the 4th-7th inning, just drop it in the comments.

Riley led the 9th inning off with his second homer of the night to make it 9-0. José Suarez got a three inning save. The Phillies Phaithful got plenty of chances to boo.

Sale and Sanchez tomorrow night on Fox. May the Braves go up sofar that I fall asleef for three innings of that one as well.