You won't find Joe Mauer listed among the American League batting leaders. After missing the first four weeks of the season with a back injury, he still falls short of the 3.1-plate-appearances-per-game qualification, and it's likely he won't reach it until around the All-Star break. When he does make his debut, it will be big news. He was batting .407 through Sunday, positioning himself to make a run at a magic mark untouched since 1941.
As good a hitter as Mauer is, no player is a favorite to bat .400. Among the reasons why no one has done it since Ted Williams are improved defense—the seven guys behind the pitcher have become better at getting to batted balls since Williams's era—and increased strikeout rates. Mauer's strikeout rate this season, about one every nine plate appearances, is excellent relative to his peers', but it is the second-highest of his career.
Here's another variable that could work against a .400 finish: his home run spike. Mauer has already set a career high with 14 bombs. There's a whiff of a fluke to that total; coming into this season, Mauer had one homer for every 10 fly balls he hit. This year, that number has increased dramatically, to one in four. Even accounting for the possibility that Mauer may have finally developed a consistent power stroke, it's unlikely that he can sustain that rate. Any significant slippage could mean a handful of fewer hits, or the difference between hitting .400 and not hitting .400.
As with his power spike, Mauer's batting average on balls in play (BABIP) is well above his career standard, and that could also spell trouble. He had a .342 BABIP coming into this season; at week's end it was .412, a figure second only to that of the Mets' David Wright. (The league average was .296.) While performance on balls in play is something that a hitter can improve, a 70-point jump most likely entails some luck and thus can be expected to fall. A typical league-leading mark is just below .400.
With the expectation that Mauer's home-run-to-flyball rate and BABIP will normalize, the safe bet is that his batting average will slip under .400. So why should we believe that this particular run at history might succeed? Because records aren't set in normal seasons. Records are set when performance meets opportunity with some good fortune thrown in. All those magical milestones that we remember, that we revere—Williams's .406, DiMaggio's 56, Bonds's 73, Gibson's 1.12 ERA—have nothing to do with normal. Respect the math, but keep one eye on history, especially when it involves a unique talent such as Mauer's.