Most people presumed Cliff Lee would be a good fit for the Mariners when they acquired him this off-season. When an abdomen injury pushed his season back a few weeks, the condition alleviated some of the buzz surrounding him. Lee is five starts into his 2010 season and still people seem to look elsewhere when discussing the best starters to date. That’s a mistake. Not only is Lee pitching well; he’s pitching better than he ever has before.

Lee is averaging a little over seven innings per start, which totals 36.2 innings pitched. He’s struck out 32 batters and walked one. That would be a strikeout-to-walk ratio of 32, which is simply unheard of. The best strikeout-to-walk ratio in baseball history (for pitchers with at least 100 innings in a single season) is 11 – posted by Bret Saberhagen in 1994. Ben Sheets‘ 2006 season is the only other case of a double-digit strikeout-to-walk rate for a starting pitcher with at least 100 IP.

Aside from Saberhagen and Sheets, Curt Schilling is the only other pitcher to break the 9 K/BB barrier, which is fitting. During Schilling’s later years with the Diamondbacks, ESPN would always joke about whether Schilling’s win total would exceed his walk total. Now, Schilling never actually accomplished the feat, but Lee very well could. In fact, Lee actually has more wins (two) than walks at this moment – and given his performance to date, should have more wins, if not for lousy run support and other factors beyond his control.

Also, Lee has yet to allow a home run. That tidbit, combined with the walks and strikeouts, make his 3.44 ERA look absurdly high. Lee’s batting average on balls in play (BABIP) allowed is .341. That’s well above league average around .300 as well as his career norms, and should regress given that he’s supported by one of the best defenses in baseball, in a park that suits left-handed pitchers very well.

Lee’s FIP – which takes defense out of the equation – is a microscopic 1.44. His xFIP – which normalizes home run rates (i.e. attempts to strip out even more luck) – is a still excellent 2.93. Lee’s Cy Young winning xFIP was 3.57. Last year it was 3.69. He’s about a half run per nine innings better than when he was considered one of the best pitchers in baseball.

Now, don’t expect Lee to pitch quite this well all season; history tells us his walk and home run totals can’t stay this low forever. But he’s still a true elite pitcher, and can reasonably be mentioned in the same breath as Roy Halladay, Tim Lincecum, Ubaldo Jimenez and other star hurlers. Unless the plan is to ship him away for future help in deep keeper leagues, there’s no reason to trade or bench Lee. Instead, appreciate how great he really is.

Oh, and give kudos to the only batter Lee walked this year: Evan Longoria.

For more on Cliff Lee and other aces, check out Bloomberg Sports’ Fantasy Tools.