AaronGleeman.com

Whatever slim playoff chances the Twins have left took a big hit earlier this week when Justin Morneau was diagnosed with a stress fracture in his lower back. While the injury doesn't require surgery, he'll miss the remainder of this season and doctors have advised Morneau to rest for the next three months before doing any running or weight lifting. "He needs the time off so he doesn't jeopardize his career," hitting coach Joe Vavra said. "Basically that's what we were looking at."

Morneau revealed that he's been playing through the back pain for 3-4 weeks, which helps explain the brutal 12-for-87 (.138) slump that he went through during that time. Of course, fading down the stretch is nothing new for Morneau, who finished last year in a similar 11-for-64 (.172) slump and batted just .220/.305/.355 during the final two months in 2007. Even when Morneau hit well down the stretch in his MVP-winning 2006 campaign his power was modest, and the monthly splits for his career are extreme:

             AVG      OBP      SLG      OPS
April       .286     .348     .521     .870
May         .305     .380     .570     .950
June        .286     .345     .499     .844
July        .307     .378     .572     .950
August      .250     .327     .443     .770
September   .251     .323     .413     .736

In each of April, May, June, and July he's hit at least .280 with an OPS above .840 for a combined mark of .297/.364/.543 through four months. Then in August and September he's hit just .250/.325/.429. His strikeout and walk rates have basically remained constant during the second-half fades, but Morneau's power has dropped 27 percent in August and September while his batting average on balls in play has fallen 32 percent for an overall production decline of about 15 percent.

Whether that's all the result of injuries and wearing down physically or there's something else at play is difficult to say, but his career-long numbers are impossible to ignore and his late-season performance during the past three years has been particularly dreadful. If you add up Morneau's final 50 games from 2007, 2008, and 2009 he's hit a combined .236 with 17 homers in what is essentially one full season's worth of playing time.

Despite the up-and-down nature of his performance Morneau has been hugely productive offensively in each of the past four years, ranking 8th, 27th, 8th, and 12th among American League batters in Runs Created (although this season's ranking will drop steadily over the next three weeks). And regardless of league from 2006 through his being shut down this week only five first baseman and 17 total hitters have racked up more Runs Created than Morneau with 434.

Ultimately it matters little whether someone hits well early and poorly late or vice versa, because a win in April or May counts the same as a win in August or September. However, struggling down the stretch is a sure-fire way for any player to turn a fan base against him and in Morneau's case the big question is whether something could have been done to avoid his late-season collapses. We'll never know, of course, and right now just getting him back to normal for even April through July of next year is the goal.