In 2007, the Seattle Mariners had quite a remarkable season. They won 88 games despite being outscored by their opponents 813-794. They ranked 7th in the American League in on-base percentage, 7th in slugging, and 10th in ERA.
On July 31, 2007, the M's were 4 games out of 1st place in the AL West with just a +1 run differential (506-505). Seattle was on the fringe of playoff contention, but with an obviously sub-par team. In spite of this, they did nothing at the trade deadline.
Not surprisingly, the Mariners finished the season 6 games out in the West as well as the wild card. Looking at Seattle's run differential, as well as at the offensive and pitching rankings listed above, most statheads like me would agree that Seattle's season was a bit fluky and a regression to the mean would be expected in 2008.
Unfortunately, the Mariners' officials thought otherwise, as they geared up in an attempt to overtake the Angels in the AL West. Over the winter, Seattle dealt Adam Jones, George Sherrill, and 3 minor league pitchers to Baltimore to acquire Erik Bedard, the pitcher who would supposedly put Seattle over the top.
Little was done to account for the decline in ability of players like Ichiro, Raul Ibanez, and Jose Vidro, who all played big roles on a leauge-average offense in '07. To make matters worse, Jose Guillen bolted for the Royals.
In short, the Mariners acted like they had a good team in the 2007-2008 off-season, when in fact they were quite mediocre. If the front office had just looked at the 2007 run differential and taken a reality check, they could have held onto Adam Jones and their other prospects in a rebuilding effort instead of depending on Bedard, Carlos Silva, and an aging offense to carry the team in 2008.
Now look at where the Mariners are: at the bottom of the league and stuck with a lot of veteran players who can't help them in the future. And a big reason is because they refused to look at their expected W-L record (based on run differential) and based expectations off of a deceiving 2007 campaign.
The author, Aaron Yorke, is a New York Mets fan who wishes the mainstream media would pay more attention to how many runs baseball teams score.