Pat Gillick was the general manager of the Seattle Mariners in 2003. He had also been the general manager of the Seattle Mariners in successful seasons previous, and in 2003 his team looked strong again. Yet the Mariners more or less stood pat at the trade deadline, acquiring only Rey Sanchez for infield depth. Gillick was somewhat famously at home in Toronto at the time, which fans interpreted as a sign of indifference, although it's unclear how being in Toronto might've left Gillick incapable of making a move. In 2003, there were computers and phones.
Fans had been clamoring for a move, and they couldn't stand Gillick staying the course. To this day Mariners fans wonder what might have been, as those 2003 Mariners wound up missing the playoffs. But the night before the trade deadline, the Mariners were 65-42, on top of their division and in possession of baseball's best run differential. The Mariners finished 28-27, ending up behind Oakland, but at the deadline they looked as strong as anyone.
Fans of contending teams fall in love with the idea of a significant midseason trade. Everybody wants their team to be involved in the trade-deadline frenzy, and it's undeniably thrilling to see your team get connected in rumors with some of the best available names. Here's a good player on the market. Wouldn't it be great if your team got a good player from the market? He would make the team one good player better! And then the team would have a better chance of winning the World Series.
It's important to have a good offseason, because a good offseason sets the foundation. Then, over the course of the first three or four months, strengths and weaknesses are revealed. The time before the trade deadline presents an opportunity for contending teams to address any weaknesses. Teams that don't, or teams that don't make a splash, don't score as well with their fans as teams that do.
Obviously, adding talent helps in the short term. Let's define a contending team's talent level as being X. Let's say that in July, that team swings a trade for a player of positive value Y. Let's say that, in acquiring that player, nothing of significance was lost from the major-league roster. Now, instead of X, that contending team has a talent level of X + Y, whatever Y might be.
Everybody understands that. What's critical, though, is understanding what kind of impact you can expect an acquisition to have. And I think this is the key to keeping yourself sane. I know pretty much all of the issues people have with Wins Above Replacement as a statistic, but let's use WAR going forward, just for the sake of making things easy. Let's say that teams have 60 games left in the season come deadline time, or a dozen starts for a starting pitcher.
Since 2009, 437 different position players have batted at least 500 times. According to FanGraphs, not a single one of them has been worth at least three wins above replacement per 60 games. Only 28 of them have been worth at least two wins above replacement, and those are basically your franchise superstars. Guys who very seldom get traded. Meanwhile, since 2009, 256 different starters have thrown at least 100 innings. According to FanGraphs again, not a single one of them has been worth at least three wins above replacement per 12 starts. Only 11 of them have been worth at least two. Superstars, again. Aces. Very rare trade candidates.
Let's say that, for whatever reason, you think your team could acquire Felix Hernandez at the end of July. Let's forget about Felix's remaining years of team control and focus on 2012. If Felix were replacing a replacement-level starting pitcher in the rotation, you'd expect to be two or two and a half wins better for it over the rest of the year. That's it. And acquired starters usually aren't replacing replacement-level starters.
There is the playoff impact, and that can't be discounted. A team that gets better down the stretch and makes the playoffs is also better in the playoffs. But it used to be that a team's time in the playoffs could be as short as three days, and now it could be as short as one day. We're talking about player impact over very brief windows of time. Players can be expected to make only a limited impact.
There's also the matter of in-season leverage. For contending teams, the remaining games are "higher-leverage games" than the games that've been played so far. In the same way that the seventh through ninth innings of a close game are higher-leverage innings than the first six. That's another consideration; every win and loss does matter just a little more.
But, on average, an acquisition can be expected to do only so much. A superstar could mean just a few games. A regular player, a run-of-the-mill helpful player, might mean one game, or even nothing. There is a fraction of the season left to go. Only so much can be accomplished over the remaining fraction.
You might cite the 2003 Minnesota Twins as an example of a team that was energized by a midseason trade, when the Twins picked up Shannon Stewart. The Twins were 44-49 at the All-Star break. Then they picked up Stewart and finished 46-23. Stewart even managed to pick up considerable MVP support. But Stewart's level of performance didn't meaningfully change, and all we can prove is correlation. What about the 52-51 Cleveland Indians, who added Ubaldo Jimenez and finished 28-31? Sometimes teams play better, sometimes teams play worse, and sometimes teams play the exact same.
That's a huge factor to remember here: sample size. What's left of the season is a pretty small sample size, once the deadline rolls around. There's a lot of fluctuation around small sample sizes, and any player's expected performance comes with enormous, wide error bars. There's no guarantee that a big-time player will produce like a big-time player down the stretch. There's no guarantee that a small-time player won't produce like a big-time player down the stretch. There's no guarantee that a team that remains the exact same won't over-perform, or simply play better. The less of the season that remains, the more is left up to chance. Put another way, the less of the season that remains, the more power is stripped away from team executives.
It's helpful to make a helpful trade. The most you can ever do is base a decision on probability, and if a team adds a contributing player, then the probability is that the team will be better for it. Down the stretch, and in the playoffs, should the team make it. I'm by no means opposed to the concept of a midseason trade. But one has to understand the limited significance of most midseason trades. There are no cure-alls, there are no players who can put a team "over the top." There are only boosts that might not even work out to be boosts over one or two months. Think about how much a deadline rental might realistically mean. Think about how many years of control an organization has over a quality prospect. Oftentimes there's nothing wrong with making a trade in July, but oftentimes there's little wrong with not. These moves usually just don't mean that much.