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.

Denard Span ranked 28th on my inaugural list of the Twins' top prospects in 2007 despite coming off a season in which he hit just .285/.340/.349 at Double-A, and then narrowly missed my top-40 for 2008 after batting just .267/.323/.355 at Triple-A. At that point he was still relatively young at 24 years old, with good speed and athleticism, but the former first-round pick had racked up 2,184 plate appearances spread over five seasons in the minors and was a career .283/.348/.348 hitter.

Prior to last year I wrote that "there's little in Span's minor-league resume to suggest future big-league success" and actually tried to show optimism by opining that "even modest improvements could make him an option as a reserve outfielder." Less than two years later Span has established himself as not only a big part of the Twins' future, but as one of the best all-around players in the entire league. I'm not quite sure how to explain Span's transformation from bust to star, but he's made a believer out of me.

It didn't seem especially significant at the time because of his long track record of mediocrity, but Span quietly started to turn things around during the second half of 2007. He hit .306/.371/.393 with improved strike-zone control at Triple-A following a miserable first half and then turned things up another notch back at Rochester last year, hitting .340/.434/.481 with vastly improved plate discipline and power in 40 games. At that point my view of Span's potential began to change, but what came next is still a shocker.

Called up to Minnesota for good in late June, Span was in the starting lineup for every single one of the final 81 games and batted .294/.387/.432 in 411 trips to the plate. He smacked six homers after going deep a grand total of seven times in 509 minor-league games coming into the season and posted an outstanding 60-to-50 strikeout-to-walk ratio after striking out nearly two times for every walk previously. Toss in excellent outfield defense and Span ranked fifth on my ballot for team MVP as a rookie.

There was a healthy bit of skepticism regarding how Span would fare this year, but he's looked nothing like the pre-2008 version and has basically duplicated his fantastic rookie performance over the course of a full season. He's batting .310/.394/.419 in 127 games, producing the league's ninth-best on-base percentage while again posting a strong strikeout-to-walk ratio at 80-to-65. His defense in center field has statistically graded out poorly, but as a corner outfielder his glove continues to get excellent marks.

Basically, he's a stud. Span has hit .304 with a .391 on-base percentage and .425 slugging percentage through 220 career games, rates as one of the elite defensive corner outfielders in all of baseball, can play center field without embarrassing himself when needed, has shown absolutely zero platoon split against left-handed pitching, and at 25 years old is under the Twins' control for another five seasons. Here's how his batting average and OBP rank among all outfielders since the beginning of last year:

                     AVG                             OBP
Ichiro Suzuki       .330        Manny Ramirez       .428
Manny Ramirez       .323        Matt Holliday       .402
Matt Holliday       .318        Adam Dunn           .397 
Carlos Lee          .310        DENARD SPAN         .391
Magglio Ordonez     .306        Bobby Abreu         .385
DENARD SPAN         .304        Brad Hawpe          .383

Span has the speed that conventional wisdom craves in a leadoff man, with the added bonus that he's actually an ideal fit atop the lineup. He takes tons of pitches, draw walks in bunches, and is one of only 12 players--regardless of position--with a .300 batting average and .375 on-base percentage over the past two seasons. The others? Albert Pujols, Manny Ramirez, Joe Mauer, Hanley Ramirez, Chipper Jones, Kevin Youkilis, Matt Holliday, Miguel Cabrera, David Wright, Nick Markakis, and Derek Jeter.

Of his 215 career starts he's played right field 98 times, center field 72 times, and left field 45 times, but Ron Gardenhire indicated recently that he'd like to keep Span at one position beginning next season. In doing so Gardenhire didn't specify which position he'd prefer as Span's long-term home, but my hope is that he ends up in left field. According to Ultimate Zone Rating per 1,400 innings Span's defense has been 12 runs above average as a corner outfielder and 15 runs below average as a center fielder.

The true gap likely isn't that extreme and there's some sample-size issues at play because we're only talking about a grand total of about 1,900 innings spread over three positions, but having watched him for two years now I'd agree that Span is an elite corner outfielder and a mediocre center fielder. Moving him to center field full time makes sense if the Twins are absolutely convinced that Delmon Young has a significantly brighter future than Carlos Gomez, but my view is the opposite.

The jury is still very much out on both Young and Gomez offensively, but we already know that Gomez is an excellent defensive center fielder and Young is a terrible defensive left fielder. By playing Gomez and Span together the Twins would guarantee themselves a very good defensive outfield, which is key for a team that constantly talks up the importance of strong defense and almost always features a staff filled with fly-ball pitchers. It's tough to see a Young-Span-Michael Cuddyer alignment being a strength.

Wherever he ends up defensively the Twins are incredibly lucky to have Span atop the lineup, because his high batting average, patient approach, and fantastic on-base percentage make him a near-perfect fit there and if not for his presence Gardenhire would no doubt be tempted to put two light-hitting middle infielders with awful OBPs in front of Mauer, Justin Morneau, and Jason Kubel. Span has emerged as one of the Twins' most valuable building blocks and I'm thrilled to have been so wrong about him.