The Blue Jays are reportedly close to signing Darren Oliver, which gives me an excuse to write about him. Darren Oliver has been in the majors for eighteen years, and it would be nineteen had he not missed all of 2005. You might think that's a long career, and well, you're absolutely right. Since 1901, there have been just 106 pitchers to appear in at least 18 seasons, and Oliver is now one of 'em.
He broke into the majors in 1993 with the Texas Rangers, throwing a total of 3.1 innings. Since then, he's appeared in 654 games spanning his career, 229 of which he started. Oliver's career as a starter, at first glance, was pretty mediocre. Opposing hitters owned a .290/.360/.462 total slash line against Oliver in his starts, which -- not accounting for park/league factors -- is Ron Santo-esque. But the thing is, park/league factors are of paramount importance, especially for a guy like Oliver. He spent a lot of his time in hitter-friendly stadiums, in an era dominated by offense, and his numbers were accordingly bloated. Just perusing Fangraphs' WAR column for Oliver's years as a starter, you can see that he really wasn't all that bad.
With the exception of one start with the Los Angeles Angels in 2009, Oliver has been a full-time reliever since 2006. And here's where things get interesting. In each of the last five seasons, Oliver's posted progressively better ERA+ marks, from 120 in 2007 all the way up to 195 in 2011. At age 40 this season, Oliver set a career-high in ERA+; additionally, he's maintained a 4.19 strikeout-to-walk ratio over the last two seasons, despite never having previously exceeded 4.00 in a single season.
Using admittedly arbitrary endpoints, you can see some historical significance in what Oliver accomplished this season: he became just the seventh 40+ year old pitcher since 1901 to post an ERA+ of 195 or higher (min. 50 innings pitched). The other pitchers to do that: Red Ruffing and Hoyt Wilhelm, both of whom are Hall of Famers; Mariano Rivera; Roger Clemens; Trevor Hoffman; and hey, even Doug Jones had a very good career.
As a left-handed reliever in a thin LHRP market, it's easy to see why he appeals to some teams -- especially considering the season he just had. It's looking like we're in store for a nineteenth season from Oliver, which is pretty remarkable. He hasn't had a fantastic career, and the numbers don't really jump off the page --103 ERA+, 4.60 FIP -- but he's certainly had a pretty interesting career (during which he's accomplished a lot), and he's done so in a relatively quiet manner.