(So tweets Joe Christensen.)
Not that I'm happy about it, but I've suspected this might be the case for a while. (And it's not the first time the Twins have had a Canadian corner infielder come down with back problems.)
I've read some people (LEN3 in particular) dismiss the difficulty of playing 162 games at first base, but all those games on turf add up eventually, regardless of which position you are playing. Sure, playing first base is easier on your body than other positions (certainly a lot easier on your body than catching), but that doesn't mean it's easy to make it through 162 games without getting injured or wearing down at all.
Maybe Morneau was so outspoken about the Twins getting additional help because he was expecting to wear down in the last two months for the 13th season in a row. For all the promise he usually shows at the beginning of the season, he's never hit more than 34 HR in a season, and has averaged just under 30 HR for the last four years. That's great, but there are 14 players in baseball who have had more home runs over that span. It's not like he's a bad player by any stretch, I just don't understand how he gets so much MVP love. (By contrast, Joe Mauer has the second-best batting average in baseball over that time span, fourth-best OBP, and he plays catcher.)
Anyway, at this point in the season, the Twins' chances at the playoffs are essentially zero and they should focus on getting Morneau healthy. From my standpoint, I want to see Mauer get some nice, round, meaningless numbers to help bolster his MVP candidacy. Some markers he could reach:
30 HR -- He's at 27 now. If he breaks 30, he might out-homer Morneau for 2009.
100 RBI -- He's at 84 now. This is going to be difficult with only one good OBP guy hitting in front of him, just like it's been pretty difficult all year. (Also, some IBB's--IBB's that gave Morneau a shot to hit with an extra man on base--in RBI situations have hurt his chances for a gaudy RBI total.) 16 in two weeks is probably too much to ask, but 3-4 HR in the right spots could go a long way towards those 16 RBI.
Batting title -- He's sitting in first now, with a decent, but not insurmountable lead over Ichiro. It would be surprising if he finished any worse than second in average in the AL.
.362 average -- He's at .366 now. .362 is the best average ever by an AL catcher. .362 is also what Piazza hit in '97, the best batting average by a catcher post-WWII.
.367 average -- This is Babe Phelps' record for the best batting average post-1900.
Even if he doesn't get all of these, I think Mauer's got a legit shot at getting the MVP award. There's not all that much of an East-coast bias for the MVP since each market gets equal representation in the voting. But if he can win the batting title, hit 30 HR, drive in 100 RBI, while playing strong defense at catcher, I think he can win over a fair number of voters who don't care much about modern stats. Without the round numbers, I fear that he'll lose out to someone who had better teammates this year.

At least I'm not the voice crying in the wilderness about Morneau anymore (till he starts hot again next year).
I was looking at the AL HR race, and happened to notice that Joe is ~100 AB behind Tex. And then I noted that Joe could go into a horrendous 0-for-100 slump and still be batting .300, comfortably above Tex's .280
Baby Jebus would also have to be paid 1.9 times the amount he will actually make over the last 13 games to merely equal the Yanquis' remaining monetary commitment to Tieixieiria this year.
Love that spelling of Tieix.
I tend to think Morneau's late-season issues are based in more of a mental block. Given the guy's extremely superstitious tendencies, I find it pretty likely that stuff like this gets in his head and hampers his performance.
So he chokes late in the season, but not in other clutch situations? I'm not buying that at all.
He doesn't have a history of choking in "other clutch situations." He started building a reputation for fading down the stretch after his late power drop-off in 2006 and his complete production drop-off late in 2007. My theory is that this reputation is getting into his head and he seems like the type who can really start to overthink and press when things get clouded up mentally.
What I'm not buying is that he breaks down physically every year after playing regularly at the field's least strenuous position for four months. That would suggest to me that he is extremely poorly conditioned.
Or maybe he needs some greenies. Just sayin'.
Considering that he's on the DL for an injury now, I think it's a lot more likely that he's had back problems in the past, but they were only bad enough to hurt his production and not bad enough to put him on the DL. And I don't think that has a lot to do with conditioning, really. Koskie (another guy with a bad back) had fairly bad numbers in in August/September, though not as bad as Morneau.
From 2006-present, Morneau is 6th in all of baseball in games played. None of the guys ahead of him play on turf at home. (And are there even any turf fields left in the NL?) Lyle Overbay looks to be the closest to Morneau in terms of playing on turf, and he's about 60 games behind Morneau.
Morneau's not really a terribly athletic guy, and he plays 90 or so games a year on turf. I don't think it takes bad conditioning to break down under those conditions, especially if it's something like a bad back.
Ubes, Mauer can't win the MVP if the Twins don't make the playoffs. /bertism
Morneau is out for the year (via twitter)
JoeCStrib Morneau has a stress fracture in his lower back (L5) and is out for the season. Recovery time is 3 months.