Nick Johnson's career has become one of the major oddities of professional baseball over the last decade. Johnson debuted in 2001 with the New York Yankees, and after mediocre seasons in 2001 and 2002, Johnson broke out in 2003. He became more selective and made more contact, resulting in a much higher walk rate (17.8% vs. 11.3% in 2002) and a much lower strikeout rate (17.6% vs. 25.9%). We see the impact of these rates in his slash line statistics, as a .243/.347/.402 season in 2002 became a .284/.422/.472 line in 2003.
Fast forward to 2009. Johnson's walk rates have remained fantastic since that 2003 season with New York, bottoming out in 2004 at 13.7% (vs. a league average of 8.7%) with Montreal after an offseason trade. High OBPs and above average fielding (+3.3 UZR/150 career) carried Johnson to seasons of 4.6 and 5.3 wins respectively in 2005 and 2006. Johnson's career never jumped to superstardom because of injuries, which forced him to miss siginificant time in both 2004 and 2008, and all of 2007.
In 2009, Johnson has remained mostly injury free, playing so far in 114 games. His OBP skills have not missed a beat, as he remains among the league leaders with a .421 OBP between his time with the Washington Nationals and the Florida Marlins, whom he was dealt to at the trading deadline. As might be expected given his injury history, his defense has declined quite a bit, and his UZR this year is quite low at -6.4.
What's odd for Johnson this year is his power production. Johnson has never been a severe power threat, especially as first basemen go. He's only topped 20 HRs once (2006), and that same year was the only one in which he eclipsed a .500 slugging percentage, and he's created his .370+ wOBA's mostly from his OBP skills. Johnson's SLG usually sits about 50-70 points above his OBP. This year, however, Johnson's SLG is actually 10 points below his OBP. Usually, players with OBPs greater than their SLGs have extraordinarily low SLG, as opposed to extraordinarily high OBPs. In fact, since 1901, only there have only been 40 seasons in which a batting-title-qualified player's OBP was greater than .420 and his SLG was less than .420.
Still, offensively, Johnson is a very productive player despite this anomaly. An average player makes outs at a frequency 7.8% higher than the frequency at which Johnson does. Regardless of whether those non-out PAs are homers, doubles, singles, or walks, whatever it is that Johnson is doing makes his team better. As a result, Johnson's wOBA is a tremendous .370, comparable to such sluggers as Carlos Pena (.374 wOBA, .538 SLG) and Raul Ibanez (.375 wOBA, .548 SLG).
Nick Johnson hits the free agent market in 2010 on pace for a 2.0-2.25 win season, coming off injury. His winter will certainly be a very interesting one.