B.J. and Justin Upton are brothers. They’re also both Braves, thanks to the November signing that brought B.J. to Atlanta and the trade last week in which Justin joined him. As one would expect, the Uptons are excited about the opportunity to be big-league teammates, which they’ve been hoping to have for years. Here are some quotes from a couple of the many stories written about the Uptons in the wake of the trade:

"We've talked about playing together since we were kids, but the way our contracts and ages worked out, I never dreamed it would happen this early in our careers," B.J. said. "I'm excited to play some good prime years with [Justin]."

"It made my workout pretty easy that morning," B.J. Upton said. "I don't know how many guys get up at 6:30 and they're happy. But I was that morning."

"We'll definitely push each other," B.J. Upton said. "It's just kind of understood.”

"I didn't think it would happen this year," [B.J.] Upton said. "You don't get that lucky. But for us to have that chance now, it's tough to really put into words how it feels. We're excited about it and looking forward to it."

Over the past few seasons, both Uptons have been accused of being lazy, lacking effort, or not seeming sufficiently gritty. Maybe they’re actually guilty of those things, or maybe some combination of nature and nurture has bestowed upon both of them the deceptive appearance of not playing as hard as possible. Makeup, effort, or attitude problems are a convenient way to explain why two players who were each once ranked the second-best prospect in baseball have yet to become superstars, as well as why they’re some years removed from their most productive seasons despite being in or just entering their primes.

But now those players are excited, planning to push each other, and happy to get up to exercise at the crack of dawn. And it’s all because of a brother. If clubhouse chemistry exists—and more importantly, if it has the potential to positively impact performance—then it seems logical, at least, that no one personnel move would have a greater potential to improve a given player’s performance than adding his brother to his team. As one of the articles linked above put it, after listing some of the Uptons’ stats, “Now playing in the same outfield, those numbers could get even better as a result of classic sibling rivalry.” So has there been any performance boost associated with siblings in the same clubhouse in the past? And if so, can we say whether the Uptons are about to experience the same?

About 100 brothers have been teammates in the majors. I limited the sample to hitters who’d had brothers on their teams. But to qualify, the brothers had to fit a few other criteria. First, they had to have played together after 1950, the furthest back PECOTA is set up to retroject. Second, they had to have had some major-league experience before becoming teammates, both because we can’t retroject decades-old seasons based on minor-league data alone and because we need a no-brother baseline for comparative purposes. (Eddie O’Brien played for the Pirates in 1953 and from 1954-8, all seasons in which his brother Johnny also played for Pittsburgh. There’s no way to tell whether Eddie, who hit .236/.288/.269 lifetime, would’ve been even worse without his brother around.)

Third, I counted only the first season that two brothers played together (except for a couple cases where one of the brothers made only, say, two plate appearances in that first season, and I counted their second season together instead). If there is some sort of “brother boost,” it would show up in the siblings’ stats in the first season that they shared a clubhouse. After that, the brother-boosted stats would produce a partially brother-boosted PECOTA, and we’d no longer be able to isolate the effect of the warm fuzzy feelings.

Finally, I disqualified a couple other brothers due to unique circumstances. For example, Tony Conigliaro’s 1969 comeback from the fractured cheekbone, dislocated jaw, and damaged retina that eventually ended his career was also the first year he played with his brother Billy. Tony wasn’t the same player that season that he had been from ’64-7, but it doesn’t seem fair to blame Billy for that.

Paring down the list left me with 31-player seasons, ranging from Frank and Milt Bolling in 1958 to Jerry and Scott Hairston in 2010. For each of the 31, we generated a retro PECOTA projection for the season in question based on his performance in previous seasons. Then we compared those projections to the actual stats. Weighting by the projected and actual plate appearances for each player, here’s what we get:










The first thing to note is that this must be a very good group of hitters: league average for TAv is always set at .260, and PECOTA projected these players to be much better than that. And it is a very good group of hitters, one that includes six Hall of Famers, four non-Hall of Famers who won MVP Awards, and seven other players who had at least one top-10 MVP finish. The Uptons are the latest in a fairly long line of star-level players who played with a sibling at some point.

The second thing to note is that as good as PECOTA expected these hitters to be, it still underestimated them by a sizeable margin. In their first seasons playing together, the brothers collectively beat their TAv projections by a full 15 points. Is that proof that the brother boost exists? No, probably not. But it’s consistent with the theory, so it doesn’t contradict the notion that all that excitement the Uptons are feeling might actually mean something.

Just for fun, let’s take a look at the biggest positive gaps between projection and performance

George Brett, 1980
Projected TAv: .297
Actual TAv: .392

Brett entered 1980 with a career .299 TAv, including a .293 mark in 1978. That was plenty good—Brett could’ve been a Hall of Famer if he’d just kept doing that for the next decade—but he broke out in a big way that season. Maybe it was the mostly mythical age-27 effect, maybe it was the .368 BABIP that he never came close to matching again, or maybe it was in part the presence of Ken Brett, a then-31-year-old reliever on the Royals and George Brett’s brother, whom he’d never played with before. After Kansas City traded for Ken in August, George hit .395/.470/.659 down the stretch.

Ken Brett, by the way, pitched 13 innings for the Royals that season that without allowing a run, despite awful peripherals. It was a good year to be Bretts. The next season wasn’t so kind: George declined to a lesser level of greatness, and Ken’s career was over after another 32 1/3 innings.

Jason Giambi, 2000
Projected TAv: .284
Actual TAv: .365

This was Giambi’s MVP year, which came after brother Jeremy was traded to Oakland in mid-February. Jeremy improved a little, but Jason nearly doubled his previous career-high WARP total. (And according to reports concerning Giambi’s 2003 grand jury testimony, he hadn’t yet used steroids at the time). The next year, together again, both brothers got even better. Then they split up in the following season, and it was mostly downhill from there.

J.D. Drew, 2004
Projected TAv: .289
Actual TAv: .342

Drew’s career year was also the end of the line for his younger brother Tim, who pitched 16 innings for the Braves that season but never made it back to the majors.

Dick Allen, 1972
Projected TAv: .325
Actual TAv: .376

Dick Allen was a hell of a hitter—only eight hitters have a higher TAv since 1950 than his .330 (min. 7000 PA). But he was never better than in 1972, his MVP season, when he hit .308/.420/.603 in a league that averaged .239/.306/.343. That was also the year that he first played, briefly, with his older brother Hank, who signed with the White Sox in September. Hank went 3-for-21 that month and 4-for-39 the next season, then retired. It seems safe to say that this one didn’t have much to do with a brother boost—Dick Allen actually hit worse after Hank arrived.

Vladimir Guerrero, 1998
Projected TAv: .285
Actual TAv: .333

Vlad’s first big season coincided with the Expos’ deadline trade for his older brother.

Hank Aaron outperformed his retrojection by 31 points in 1962, his brother Tommie’s rookie year. Jose Canseco outhit his by 30 in 1990, when Ozzie debuted. Sandy Alomar and Roberto Alomar both improved on their projections by 20-plus points in 1999, when they overlapped for many more than the seven games they’d played together for the ’88-’89 Padres, in their first big-league seasons. Felipe Alou beat his PECOTA in 1961, when Matty Alou lost his rookie eligibility for Felipe’s Giants, and Adrian Gonzalez did well in 2008, his brother and Padres teammate Edgar’s rookie year.

Some players must be more likely to get a boost from a brother on their team than others, and we won’t know if or how much the Uptons benefited, even after the fact. But it’s not crazy to suggest that they might be better together than apart.

Thanks to Ryan Lind and Colin Wyers for research assistance.

Thank you for reading

This is a free article. If you enjoyed it, consider subscribing to Baseball Prospectus. Subscriptions support ongoing public baseball research and analysis in an increasingly proprietary environment.

Subscribe now
You need to be logged in to comment. Login or Subscribe
It sure looks like both Alomar brothers benefited when they were reunited on the 1999 Indians.

What is it the control to these examples? Do all players achieve precisely their projections on the aggregate? Did you check for brothers who were reunited but one or the other did not play due to being released or injured?
Yes, on the whole the projections are very close to the observed stats. See Rob's response to a similar question the last time I used retro projections in an article ( Same goes for TAv.

Didn't look for brothers who were in the same organization but never played together.
Thanks. It is a timely article.