In 2014, the Mariners were the seventh youngest team in MLB, with an average player age right around 28 years old. However, with the signings of Nelson Cruz, Seth Smith, and J.A. Happ, each of whom is on the wrong side of 32 and will likely see substantial playing time next year, the average age of the Mariners seems to trending upward as we head into 2015.
Is this good? Bad? Largely meaningless? The Mariners do still have a not-old "core" and supplementing these younger players with "established veterans" seems like a not bad approach to try and push this team towards the next level, but is there a point at which a team is too old (or too young) to find success? To see how the average player age has influenced the M's ability to win baseball games in the past, I've put together the following graph. (For this plot, I normalized against playing time as opposed to just taking the average age of all of the players on the M's roster. For example, in 2014, Robinson Cano's 665 31-year-old PAs counted for about twice as much as James Jones' 328 25-year-old PAs.)
It does seem like there is some correlation between a team's age and their ability to win baseball games, but the variability in the results also appear to increase as a team gets older (the Mariners two oldest teams put up winning percentages of 0.716 and 0.389). Only one team (out of 19) with an average age below 28 managed to post a winning record. Conversely, 11 of the 19 teams with an average age above 28 had a winning record. The Mariners project to be ~28.6 years old, on average, in 2015. According to the graph above (and to many/most of the off-season projections), they'll probably do pretty well next year, right? The answer is, like all other answers... maybe. This graph might be somewhat predictive, but it lacks a lot of context. To understand a bit more about how the ages of the Mariners have waxed and waned over time, we can look at the following graph:
Red squares represent seasons with a winning record and blue stars represent playoff appearances.
Here, we can see that the average age of the Mariners has actually fluctuated pretty substantially throughout franchise history, spanning an average age range of almost five years. (For reference, the average age for all MLB players during this period has stayed between 28 and 29 years.) I actually think that this graph is pretty neat and does a decent job of telling the overarching story of the Seattle Mariners in a single image.
For the first decade and a half of their existence the Mariners were very young and very bad. They had five different GMs in their first 13 seasons and this lack of cohesiveness in the front office likely affected the quality of the product that was put out on the field. The Mariners didn't make many splashes in the free agent market and relied largely on building from within to try and improve their team. As a result, during the first 15 years of franchise history, the Mariners average player was just 27 years old. (For reference, in 2014, only the Houston Astros were younger than that.) The Mariners didn't put together their first winning season until 1991; their overall franchise winning percentage until that point was a pitiable 0.424. Ouch.
In 1988, Woody Woodward took over as GM in what would be the first season of his 12-year-long tenure. This front office continuity, paired with new ownership in 1992, allowed the Mariners to begin to build toward the future. You can see how the average age of the team ~steadily increases from 1989 into the 21st century. The Mariners began to supplement their young talent with older, skilled players from outside of the organization. Through a mixture of fortuitous draft picks, good player development, and relatively successful free agent signings, the Mariners were able to enjoy almost a decade of success. This culminated in a four-year span (2000-2003) where the M's compiled a winning percentage of 0.580. My oh my.
Unfortunately, their success would not last. By 2003, the Mariners roster was starting to get pretty old and creaky and their organizational depth wasn't in great shape. They probably should've hunkered down for an extensive rebuild after 2003, but Bill Bavasi DID NOT WANT TO. As a result, the Mariners had some weird/terrible rosters and made some weird/terrible moves between 2004 and 2008, trading away several of their better prospects in an attempt to patch up a swiftly sinking roster. We've all lamented this period of Mariners history many a time. Thankfully (I guess?), Bavasi did such a poor job that he was fired midway through 2008, causing Mariners fans across the world to rejoice.
That brings us to the current Mariners regime. When Jack Z took over in time for the 2009 season, a more traditional rebuild started, and the average age of the Mariners decreased for four consecutive seasons (something that had never happened before). After years of building up their organizational depth, the Mariners finally seemed to push the "Let's go for it button!" during last year's offseason and signed. 2014 saw the Mariners coalesce into something that resembled a good baseball team for the first time in about a decade. Hooray!
Looking forward to 2015, the Mariners seem poised to make a legitimate run at a 90+ win season and make their way into the playoffs. They have a nice group of talented younger players and were able to address several of their most glaring needs by signing a few older free agents. They're certainly not a perfect team, but they haven't felt this complete for years. I feel good about next season, guys. I hope you do, too.